This glossary of terms includes some words not used on this web site but which are of direct engineering interest.

Word Meaning
AC Alternating current in which the direction of the current varies usually as a sine curve
active information Constantly changing, dynamic and possibly self-organising information such as speech or social media.
AM Amplitude modulation where radio signals are transmitted by carrier waves whose amplitude (size) is modulated (change or modified) by an input signal c.f. FM
appropriateness Suitable or proper in a particular context. An appropriate model is one that is not completely true or precise but which is dependable enough to serve the purpose intended in a specific context i.e. is fit for purpose. Clearly if a model is true then it is dependable but may not be appropriate because it is too detailed and out of context e.g. quantum mechanics is not appropriate for designing bridges since it deals with a level of behaviour of a material which is too detailed. In pure science Newtonian mechanics has been replaced by Relativity Theory because the latter can deal with problems where velocities approach the speed of light. However Relativity Theory is inappropriate for bridge design
architect Architects design the form of a building to fulfil the needs of people and how it will look aesthetically. Architectural design is about the sense of space, occupancy by people, symbolism and relationship to its setting.
art Something of special or more than ordinary significance Art comes with many different forms and structures of matter such as paint on canvas, carving of wood or stone or even a large structure
as/is distinction The difference between a theory or model being used as if it is true and whether a theory actually is true.
atrial fibrillation Irregular contractions of the heart muscle
attributes Characteristic, inherent quality or feature of something. The six attributes of a process can be classified as why, how, who, what, when and where – see process.
axiom An accepted statement assumed without proof
bandwidth The smallest range of frequencies within which a particular signal can be transmitted without distortion, or the speed or capacity of data transfer of an electronic system
BIM Building Information Modelling
binary Consisting of two. Binary counting is based on 2 units (0, 1) whereas decimal counting is based on 10 units (0 to 9).
calories Units of energy. Small calories (cals) are about 4.2 joules. Large calories (Cals) are 1,000 cals.
capacitance The property of being able to store potential
chaos Utter confusion, disorder and lack of organisation.
chaos theory The study of non-linear systems which show great sensitivity to initial conditions c.f. chaos, uncertainty. These dynamical systems viewed from a traditional perspective, seem to behave randomly and yet conform to a pattern. They can reach a state where if the system is started with a set of initial conditions (A) fractionally different from another set of initial conditions (B) then after a few cycles the two behaviours become very different – this has been demonstrated both theoretically and experimentally. These results imply that there are quite severe limitations in our ability to predict what might happen in such a system – it is chaotic. Chaos theory has produced some interesting results for simple small degree of freedom problems however there is much to learn about large degree of freedom systems – applications to management theory that have been promoted are illustrative only.
civil engineer First used in contrast to military engineer. Now it applies to construction and infrastructure work.
closed system A system in which all of the sub-systems, elements or holons within it or all of the factors affecting it are precisely defined and all relationships are known. It has clear boundaries and limited and predictable cross boundary interactions. The total set of possible outcomes are known although it may be that only the probabilities that are calculable. The assumption that the sum of the probabilities across the sample space is equal to one is a closed world one – c.f. open world.
complex Complex systems are difficult to describe and predict because they have many interconnected parts with emergent properties. They may, under certain conditions, behave in a chaotic way. Complexity theory is the study of how both complex and complicated systems exhibit simple behaviours c.f. chaos theory. High complexity in a project or organisation is associated with tight spacing of equipment, close production steps, many common mode connections, a limited possibility of isolating failed components, limited awareness of interdependencies because of specialisations, limited ability to substitute, unintended feedback loops, interacting control parameters, limited understanding of social processes and tightly coupled systems. A complex system is not just complicated but may be incomplete with emergent properties from interdependencies that are unknown and unforeseen. They often cannot be ‘solved’ rather they have to be managed to desirable outcomes.
complicated A complicated system may contain lots of elaborately interconnected sub-systems or holons. To the non-expert complicated systems may seem complex but to an expert each of the subsystems may be tame i.e. understandable and predictable. There may be a sufficient experience and knowledge for dependable design e.g. for the jet turbine.
contingent Dependent on something uncertain. Used in to identify models where the uncertainty is contingent on the starting conditions as is the case for many complexity science models.
corollary Something which is a natural consequence of something else
craft Art, trade, occupation or hobby that requires special skills
damping A mechanism through which energy is dissipated
DC Direct current in which the direction and magnitude varies only slightly
dependability Being dependable, trustworthy and reliable. Practitioners require information that is sufficiently dependable for the decisions they make. Truth is sufficient but not necessary for dependability, e.g. Newton’s Laws are not strictly true in that propositions can be deduced that do not correspond with the facts for bodies travelling at velocities near the speed of light. However for all practical engineering purposes on the surface of the earth Newton’s Laws are true. Other theories are dependable only when the practitioner is aware of context e.g. elasticity in steel is dependable for small strains but not for large plastic strains. There are 4 sufficient conditions for a proposition to be dependable. 1. A highly repeatable experiment can be set up to test it. 2. The resulting state is clearly definable and repeatable. 3. The value of the resulting state is measurable and repeatable. 4. The test is successful. Note that these conditions together are sufficient but are not necessary. Deficiencies in any of these conditions result in a loss of dependability
design To form or conceive
determinate structure A structure in which we can find all of the internal forces using equilibrium.
deterministic The philosophy that all events are totally determined by previous events with no uncertainty. This perhaps rather surprisingly is the philosophy of Newtonian mechanics as used in engineering science. However the practical implementation of it in engineering is non–deterministic – see modelling, practical rigour, chaos
duty of care A duty of care is an obligation to not act negligently under the Law of Tort. An obligation to take reasonable care to avoid foreseeable harm to another person or property. A duty holder is someone taking on a set of responsibilities where there is a duty of care.
electrocardiogram A record of the changes in electrical potential in the heart
emergence A situation where an attribute of something as a whole emerges from the interactions of its parts. It is the reason why a whole is more than the sum of its parts. For example you have an emergent property of being able to talk and walk whereas none of your individual parts can do that on their own.
emergent property A property of a whole that emerges from the interactions of the parts. It is the reason why a whole is more than the sum of its parts. It is a property that applies to the whole and not to the parts e.g. an emergent property of you and me is that we can talk and walk. An emergent property of gas molecules is pressure and of steel crystals is yield strength
energy A capacity to do work – potential or kinetic.
engine cycle Engines have to provide continuous power – so they work through a series of thermodynamic processes that cycle round and round – a thermodynamic cycle that repeats itself.
engineering Turning dreams into reality – done by people for people to improve the human condition. Engineers use science to create technology
ethics The discipline of moral conduct. It is a set of standards by which a particular group or community decides to regulate its behaviour to distinguish what is acceptable in pursuit of its aims and what is not. In ordinary discourse the words morals and ethics are used interchangeably. Engineering ethics involves normative enquiries aimed at identifying and justifying morally desirable norms and standards that ought to guide us. The ‘golden rule’ is found in almost all religions in various forms i.e. ‘do unto others as you would have them do to you.’ There is no golden rule specifically for engineering but there is a duty of care to apply professional knowledge and skills responsibly. Ethics is about managing difference and making choices about individual, family, work and societal issues. Professional Institutions and society have their own rules of conduct expressed in a code of behaviour. Are ethics absolute or relative? Philosophers have failed to find any absolute rules. There is a hard core of principles with which almost everyone would agree but it seems that it is always possible to find a counter example for any general rule that places one rule over another. For example whilst being honest is an important principle there are circumstances where a white lie may be justified.
field theory A theory about a region of space in which any object at any point is influenced by a force – gravitational, electrical or magnetic
finite element method A method in which a system such as a structure is divided (in a theoretical model – not in reality) into discrete finite elements or pieces in order to find the internal forces. The elements may be any size but are usually either a whole structural member such as a beam or imaginary divisions (of a plate, wall or floor) into simple shapes such as triangles and rectangles.
flexibility The amount by which a bar or material may stretch or squash under a force.
flow Movement as in a stream.
fluid A liquid or gas that flows and changes shape when acted upon by a force.
flutter A form of inductance and a kind of self-reinforcing dynamic oscillation.
FM Frequency modulated where radio signals are transmitted by carrier waves whose frequency (rate) is modulated (change or modified) by an input signal c.f. AM
force Something that changes the velocity of a physical body
form The external shape of something
frequency The number of occurrences of a repeating event per unit time for example the number of oscillations or cycles occurring in a unit of time.
function The purpose for which something is designed to perform or the role of a person
fuzziness One of the chief structural elements of uncertainty which is vagueness and imprecision. For example the statement that ‘the stress in a beam is low’ conveys meaning, is useful, but is not very precise. Fuzzy sets were developed to allow reasoning with vague terms as linguistic variables. Thus we can form a fuzzy set meaning ‘low stress’. In classical set theory this is not possible because an element is either a member of a set or it is not. A fuzzy set has elements that have a degree of membership that varies over the interval [0,1] indicating a degree of belief that the element is in the set. Fuzzy logic is logical reasoning with fuzzy sets. A fuzzy relation is a fuzzy set that expresses a relation between two fuzzy sets and is a linguistic variable e.g. ‘approximately equals’ or ‘much greater than’. It is defined on the Cartesian product which for two sets X (containing points x1, x2,….xm ) and Y (containing points y1, y2,….yn ) is the set of all pairs (xi,yj).
grand challenge A big issue that requires a significant effort to resolve
hard system Any physical system such as a building structure or railway line which involves action and reaction c.f. soft systems that involve people. Hard systems do not depend on who is interacting with the system, they are assumed to be independent of the observer and hence are the same for all of us. Our collective understanding has developed through the physical sciences particularly those that underpin engineering such as mechanics. The parameters are measurable and the methodology is clear and the results normally quite dependable. Relationships are usually expressed as deterministic functions. They are hard in the sense that they are clear, quite precise, predictive and testable. Clearly there are hard systems problems that continue to be difficult e.g. soil behaviour and structural fatigue. Non-linear system behaviour is increasingly becoming important as we realise the limits on predictability of such systems – see chaos theory. All designed hard systems have a role in a soft system process and it is in this sense that all hard systems are embedded in soft systems. For example a beam in a building has the function of carrying loads from the floor slab and passing them onto the columns and so on down to the foundations. The steel and the concrete does not ‘know’ that that is what it is doing – the functionality is ascribed to it through the soft system process of using the building i.e. the people who have conceived it, designed it, built it and who use it. Natural hard systems such as a lake do not have designed function but they do take roles in soft system processes e.g. as part of a tourist attraction, as a water sports attraction, a habitat for a rare species of fish or as a reservoir. In the past we have failed to understand that all hard systems are set within soft systems because we have collectively failed to understand sufficiently that humans are intimately connected to their environment.
hazard A state of the world or state of affairs – a condition within a process with a potential for harm. For example, a trailing wire that someone could trip on is potential for human injury or death; a wind load is potential for damage to property; processes resulting in climate change are potential for damage to the environment; a decision that results in loss of share price is potential for economic loss; not working hard enough to pass an examination is potential for failing to meet objectives. Hazards exist in the past, present and future whereas risk exists only in the future. Hazard analysis is the systematic search for hazards in a system both hard and soft. Hazard management is the control of hazards by removing them if at all possible, reducing them by redesigning or modifying the system and finally by remedying them so that the risk is acceptable.
heat Energy transmitted from an object at a higher temperature to one at a lower temperature
hierarchy Levels of description of a system so that at each level the lower levels are subsystems of the higher levels so that it describes systems within systems within systems. Evolution in complex systems leads to differentiation in multi-level hierarchies. A hierarchical model is a graphical representation of a concept or idea in the form of a hierarchy.
holistic The idea that the whole is more than the sum of its parts
holon Anything considered, at the same time to be both a part and a whole. It has emergent properties that derive from the co-operation of the parts e.g. a beam is a whole (with properties of size, strength and hardness that derive from the molecules of which it is made) and it is a part (as it contributes to the structure in which it is embedded). A soft system example would be yourself. You are a part – of your family, your neighbourhood, your country etc and yet you are also a whole made up of parts or sub-systems i.e. your skeleton, the bones and muscle that make your structural subsystem, your nervous subsystem i.e. brain, nerves etc and thought these are hard systems we can only understand through soft systems – us. The attributes that are you e.g. a good sportsman or a happy person with a positive attitude, emerge from the co-operation of your subsystems.
impedance The opposition to a flow – capacitance, inductance and resistance
impelling proposition A statement that can create a collective drive or urge to a central common purpose – it expresses the vision of a team, group or organisation e.g. for a water company it might be ‘supplying clean, fresh, safe water
incompleteness That which we do not know. In any model there will be some things that are purposely excluded and others that perhaps should be included if only we knew they existed. This is an aspect of risk often ignored in formal methods because the theory of probability requires that everything in the sample space be identified and the probabilities sum to unity. Managing incompleteness i.e. the unforeseen and unexpected is the biggest challenge in risk management.
indeterminate structure A structure in which we cannot find all of the internal forces using equilibrium – we have to use a theorem that states that a structure in equilibrium has a minimum of internal potential (strain) energy
inductance The storage of flow
induction 1.      The process by which flow produces potential without contact.

2.      Estimating the validity of a whole from observations of parts.

inertia The property of mass by which it retains its velocity when not acted on by a force
infrastructure The underlying framework underpinning all of the facilities, services and installations needed for a community, society, city, region or nation to function. It includes buildings, roads, railways, aviation, ports, communication and energy (electrical power, gas) plant and distribution networks, water and food supplies, waste disposal, flood and coastal protection, emergency services, housing, public institutions such as schools and hospitals and even prisons
ingeniarius The Latin root of the word engineer meaning someone who is ingenious in solving practical problems.
integrated circuit A complete electronic circuit manufactured as a single unit.
intelligent consumer Consumers who understand sufficient of how some object works to be able to specify what they need and want and to ask questions of the vendor.
intentionality People have intentions – they decide what they want and when they want it. The motivation behind their decisions is rarely obvious and usually very difficult to identify. The principle attributes of a hard system are action and reaction. A soft system has the extra element of intentionality. It’s a bit like throwing a stone in the air (a hard system) but where the stone has a mind of its own and decides to change its trajectory in mid-flight. Relationships are non-linear with bifurcations and instabilities. This means there are inherent limits to our ability to predict soft systems – because of intentionality, an emergent property of the brain
interdependence Where two processes are mutually dependent. We humans are beginning to understand that we are interdependent with each other and in particular with the physical world and cannot continue to attempt to dominate it regardless of environmental impact – see sustainability.
intersubjective Able to be understood or used by a number of people
Italian flag Used as a colourful indicator of an interval probability. For example in p(A) = [0.4, 0.8] the interval 0 to 0.4 is coloured green (representing the evidence for success), 0.4 to 0.8 is white (representing what we do not know and 0.8 to 1 is coloured red (representing evidence for failure). Green, white and red are the colours of the Italian flag.
joule A unit of energy equal to the work done by 1 Newton moving 1 metre in the line of application of the force. It is 1 watt second
learning journey The stages of a learning journey are forming a learning identity and purpose, developing learning power, generating knowledge and know-how, applying or performing learning in authentic contexts and sustaining learning relationships.
learning organisation Learning is the knowledge and skills acquired through study. It is the changes in behaviour of an individual or organisation arising from experience. It concerns recommendations for what we need to do in the future, made on the basis of past experience. The learning organisation promotes and encourages a culture of learning, of pursuing new knowledge and not just reinforcing existing knowledge. An organisation that maintains a corporate memory to try to prevent the repetition of past mistakes
learning power Learning power is a set of learning dispositions such as learning to learn, critical curiosity, meaning making, resilience and perseverance, creativity, relationships (valuing interdependence) and strategic awareness (understanding your own learning).
mental model These are the representations, the models, in our minds. We can think of them as patterns e.g. of electrical activity in our neurons, as patterns of chemical interactions. Memories are patterns in the mind and through them we have concepts e.g. of time and identity. To the extent that we think then we are our mental models. They form our worldviews, they form our opinions and they form our understanding of the physical world. They may be wrong, they may be misconceived, they may define our willingness to pay and they are the basis of our judgements. Imagination and creativity are the result of forming new links between patterns. Through imagination we can build scenarios, think about the past and the future e.g. risks. Knowledge is a set of mental models some of which are expressible in natural language. Objective knowledge we share with others and we are concerned whether it is dependable, true or false. We reason in natural language but we also use formal languages and logic principally mathematics. Subjective knowledge is within us and deep within us the subconscious mind contains mental models that control e.g. our heartbeat. Some models can be subconscious part of the time and not at other times e.g. learned skills such as driving a car. These ideas are important in understanding engineering judgement.
messy problems Problems and situations that do not seem to yield to easy solutions. You get the feeling they are rather like sorting out a bowl of tangled spaghetti that seems to get more tangled the more you try to sort it out.
metal fatigue A deterioration of the mechanical properties of a material when subjected to a very large number of small repeated forces.
mind map A means of representing a concept, idea or topic as a map e.g. drawn on paper or computer, it is built up from a central “idea” with related ideas radiating out from the centre. The technique of mind mapping is intended as a learning aid, for remembering, understanding and developing ideas; the basic format of a “radiating linkage” of ideas can be personalised with symbols, colouring and designs.
mind-body dualism The idea that mental phenomena are not physical, that subject and object are different phenomena and the mind is separate from the brain.
mission statement A high level statement of the purpose of an organisation. The value of such a statement is often in the process of deciding what it is rather than what it actually says since the clarification of aims and purpose helps to create a common vision.
model A representation of something. It may be physical e.g. a three dimensional (3D) representation of specific aspects of something such as an architectural model of a building. It may also be theoretical e.g. a mathematical equation representing some physical process. It may be computational e.g. computer representation of forces and displacements in a structure such as a finite element model or may be graphical such as a ‘walk through’ 3D pictorial representation of the interior of a building or an oil rig. Note that as models are representations of a reality they are by definition incomplete and so describe the world only from a specific point of view. Model analysis is a process of using models combined with appropriate analytical techniques to predict the behaviour of real world systems e.g. a structure such as a dam, the behaviour of a river flow.
morals Concerned with right and wrong – with what ought to be rather than what is. They are about defining what is good. See ethics which is the discipline of moral conduct. In everyday language the words morals and ethics are used interchangeably. Philosophers argue about how to distinguish moral and non moral good. Some distinguish by content, some by whether it affects other people, others base it on religion. A moral action is one that can be morally evaluated. Our values underpin our morals and both set the context for quality – all are crucially important for successful engineering and in fighting off any possibility of corruption
necessity The state of being required to be done or achieved, imperative or indispensable. The necessities of life are food, warmth and shelter. A necessary condition is one that must be fulfilled. Condition A is necessary for condition B if B cannot occur unless A also occurs i.e. B only if A e.g. safety is necessary for good design. Also in the logical implication ‘If A then B’ or ‘A implies B’ B is necessary for A and A is sufficient for B e.g. ‘If (good design) then (safe design)’. 2. In interval probability theory using the Italian flag, necessity is a conditional measure of the degree to which success of a sub-process E is required for success of a super-process H i.e. p(H/E). It is the evidence for H given E expressed as an interval probability
Newton One Newton is the force needed to accelerate one kilogram of mass at the rate of one metre per second squared in direction of that force.
Newtonian physics Alternatively known as classical mechanics and based on the laws of motion formulated by Sir Isaac Newton (1642-1726)
object An object is anything that, by being to some degree stable or coherent, may be apprehended, perceived, understood or conceived through thought or action.
object oriented programming Programming a computer by creating ‘objects’ that interact with each other. The objects contain data as attributes and methods to process data.
objective 1. A precise statement of an intended outcome – it is a target for success in a process. An objective should be specific and you should know clearly when you have reached it. An objective should be SMART i.e. Specific (i.e. precise and clear), Measurable and Memorable (i.e. you should know when it is achieved or not and you should always remember it easily), Achievable (i.e. not totally beyond your capabilities and resources – it should stretch you but not be unachievable), Realistic (i.e. keep it close to reality and firmly grounded) and Timed (i.e. set a date and programme to attain it).

2. Knowledge and information that is not subjective i.e. exists outside the mind of anyone individual and is available to everyone. We can think of it as all of the books in the library and all of the information available on the internet. Objective knowledge has an objective existence even though it derives from our collective subjective minds. However this test of shared existence of knowledge must not be confused with the test of whether it is true or false. Objective knowledge can be fictional e.g. Sherlock Holmes, mermaids and it can be wrong or false. Engineers need objective knowledge that is dependable.

open system A system where we need to think about transfers of energy, resources, materials, equipment, information and many other forms of flow across the boundaries.
passive information Information that changes only slowly for example as the pages of a book deteriorate and become difficult to read.
personal mastery A commitment continually to clarify and develop our personal vision, to focus energies, to develop patience and to see reality. It is the cornerstone of the learning organisation. It is the discipline of personal growth which goes beyond competence and skills though it is grounded in them. An alternative phrase could be personal excellence because it derives from our personal habits. The juxtaposition of vision (where we want to be) with a clear picture of the current reality (where we are relative to where we want to be) generates a creative tension. Personal mastery is learning how to generate and sustain creative tension in our lives
phronesis Aristotle’s notion of practical wisdom and prudence
poiesis Ancient Greek word for making
potential Capable of becoming, voltage in electricity and velocity in mechanics
power The capability of influencing, energy expended over time and measured in Watts
practical rigour Often it is asserted that theory is rigorous and practice is ad hoc. This is not the case. Practical rigour is different from theoretical rigour. Practice requires a use of rational judgement that transcends strict logical rules to deal with uncertainty. Engineers create practical solutions despite the limitations of our understanding. They use appropriate models, find dependable evidence and with a vision of what is needed create solutions that work. Practical rigour requires practical foresight and analysis of all hindsight. The possible unintended consequences of human action are legion and the rigour of practice is about anticipating and managing them. The values of science are clear-cut – truth and precision – the values in engineering are many and various, hard and soft and often almost impossible to measure. Scientific rigour requires selective inattention to the difficulties with which we cannot yet cope. Practical rigour does not have that luxury it must include everything that is relevant.
practical wisdom A quality of discerning and judging – a way of looking at things with an ability to see the world in a coherent picture. It has been argued that a wise person has to have knowledge, ethicalness and appropriate skills to a high degree. An appropriate attitude with an ability to cut through to the essential goals and aims and to have the will and purpose to keep these in focus. It is to do with finding simplicity in complexity. More fundamentally it is to do with worldviews and the way a person constructs the world in which they operate, which in engineering is to do with having appropriate models to fit the situation. Practical wisdom implies practical rigour which in turn implies practical intelligence which implies practical experience. In other words practical experience is necessary for all of the others but it is not sufficient because there must be reflective learning from that experience.
process That which is done to change a state of the world. A basic tool for describing a system. It is a way of getting from where you are now to where you want to be. A process can be viewed and described from many points of view e.g. safety, functionality, cost etc. It can be used as a central idea from which all others can be ‘hung’. It is flexible and can be used to manage change. Answers to the questions who, what, why, where, when and how enable you to describe a process. Why identifies the purpose and hence drives the change in who, what, where and when through the transformations identified by how. It can be formulated as why = how (who, what, where, when) though this should not be interpreted as a mathematical formula. The output of a process may be a product but that in itself has a life cycle and is also a process. A number of process modelling tools are now available.
process model An arrangement of processes such that the lower level processes work together to achieve the purpose of the higher process. This approach to process mapping is consistent with the value management principle – deal with ‘why questions before how questions’
progressive collapse A series of failures in a chain reaction such that the consequences are large compared to the initiating damage.
purpose The reason for doing something.  The intention or objective.  The result or effect that is intended.  Purpose is the answer to the question – why are we doing this process?  The answer determines the models used.  It is a question that civil engineers often do not ask and as a consequence so often they are not able to articulate to the client the value they have added or they are immersed in interesting technical detail which is of secondary interest to the client.  This is often at the root of the reason that their work is undervalued by non-technical people.
quality Fitness for purpose and degree of excellence at the same time. We make decisions about excellence based on our preferences in the choices we make to fulfil a purpose that includes function, cost, safety, aesthetics, sustainability etc. Our preferences are based on our values. Worth is a measure of the value we give to something. Excellence is the state of having the highest worth i.e. the highest value and the highest quality. Fitness for purpose is quality – it is important to see that quality is not just about the level of functionality it is about the total purpose of a project and its context i.e. total quality. The degree of quality is a measure of how good the totality of what we are getting is relative to what we want from any process. Understanding our values is central to delivering quality – of being clear about the relationship between excellence and fitness for purpose.
quantum computing Computers that use of quantum-mechanical phenomena to perform operations on data. They use quantum bits rather than binary digits.
radiation The process in which energy is emitted as particles or waves
randomness Lack of a specific pattern in some data e.g. a ticket in the UK National Lottery. But how can we know if a number is truly random? We test any sequence, indeed any data and look for any pattern. If we find one then the information is not random. However if we search and search and find no patterns then we can become more confident. However there is no final test to establish randomness – we can only say that it seems to be random or there is strong evidence that it is random. Complex patterns do occur in random data but only over populations and it is these patterns that are studied in probability theory and statistics. If there is no pattern even in a population then everything has an equal chance and that represents a state of maximum information entropy or maximum disorder in the information. Randomness is only one aspect of uncertainty but it is the only uncertainty represented in probability theory. Both have been used extensively in e.g. reliability theory and so is relevant to uncertainty in engineering problems
reading an object Observing, understanding and interpreting an object to give it meaning.
reflective practice Acting with practical wisdom and rigour – the way professionals do their work. They perceive the world, they reflect upon it and they act. They do it with rigour, wisdom and foresight. Practitioners need to reflect critically on what they do and the decisions they make before and after the event. Much of the expertise of practical professionals lies in the ability to use these skills in action in complex and unpredictable situations.
relativity theory First developed by Albert Einstein (1879-1955) as a theory of physics based on two ideas. First that the laws of physics are the same for observers in uniform motion relative to each other and second that the velocity of light is the same regardless of that relative motion.
resilience The ability of a system to withstand or recover quickly from challenging conditions; to respond by detecting, preventing and, if necessary, handling disruptive challenges. It requires planning, learning, resources, watchfulness, co-ordination and co-operation c.f. robustness.
resistance Opposition to flow through the dissipation of energy
risk The chance or likelihood of a specific state of the world, or outcome, at some time in the future combined with the consequences that will follow and set in a particular context. Usually the state of the world is defined as an unwanted event e.g. a hazard that will result in harm. However it could be an unintended benefit that represents an opportunity to add value – see uncertainty. A risk for one person may be an opportunity for another eg risk of theft may be an opportunity for an insurance broker.  Risk depends on context e.g. the risk to the driver of a car driving at full speed on the highway is more than on a purpose designed track. It may be helpful to think about risk as a description of the degree to which evidence about the past and current state of a process together with projected future states will lead to success or failure in the future. You may describe the process in terms of activities e.g. travelling by car, climbing some scaffold; in terms of hazards e.g. a live electric wire, flooding; in terms of events e.g. an accident, industrial action or in terms of consequences of events e.g. financial loss, death. Perhaps one of the biggest difficulties is how to measure risk. Probability theory is often used but relies on a closed world model which is clearly hardly ever the case in wicked problems.
robustness Sturdy, resilient, durable and hard wearing. A system that is robust is not vulnerable i.e. the consequences of possible damage are not out of proportion to the magnitude of that damage. For example minor damage on a bridge by a car should not cause the bridge to collapse. There is little theory about robustness but it is clear that sturdiness in all limit states is important.
router Software or hardware that transfers data between computers
SA Node The sino-atrial stimulus which depolarises heart muscle cells. Depolarisation is a change from the negative charge inside a cell (compared to the outside of the cell) to a positive one that allows electrical pulses to flow.
scalar A quantity that has magnitude only c.f. vector
science That branch of knowledge that seeks to find truth
semiconductor A material like silicon that conducts electricity but not as well as a good conductor like copper.
silo – organisational Silos occur when people get trapped inside their specialist departments, social groups, teams or pockets or compartments of knowledge. Hence the integration and ‘joining-up’ of systems is problematical – data and information about interconnectivities at organizational, commercial and policy levels is poor and disjointed approaches to governance and policy create perverse incentives and conflicting actions. There are also limitations on capacity, inefficiencies, poor reliability, low adaptability and missed opportunities.
socio-physical system Any system where both social and physical issues must be considered.
soft system Human and social systems involving people. Our ability to model them and hence predict them dependably is very poor. Soft systems comprise action, reaction and intention c.f. hard systems.
structure The difference between a random pile of component objects and a functioning object. For example a building may have a structure of beams, columns and walls etc.
subjective Perceptions and private thoughts that cannot be shared. It is a concept widely misunderstood by engineers with the consequence that they tend to undervalue their own skill of engineering judgement. We reach out to the world through our senses. We hear noises, we see things and we touch them. But what is the world really like? If our eyes were sensitive to X rays we would see the world quite differently. Our mental models would be quite different. So there are perceptions and private thought that cannot be shared – they are truly subjective e.g. the pain in my stomach. However there are many perceptions that we can share and by discussion we agree about certain things – they are inter-subjective e.g. the colour of a fabric. We construct ideas and relationships and we measure things in ways that are repeatable and dependable and they lead to objective testable knowledge e.g. science which exists outside any one person’s mind and is therefore objective. Engineering judgement relies on experience and personal characteristics and whilst it is not easily measured and demonstrably dependable except in hindsight it is very valuable. It is not arbitrary and subjective and it is not easily measured nevertheless when it is good it is dependable and objective.
subsidiarity The idea that systems models should be created at the lowest practical level consistent with delivering their purpose.
sufficiency The state of being enough, being adequate for what is required to be done or achieved. A sufficient condition is one that, if fulfilled, is adequate. Condition A is sufficient for condition B if when A occurs then so will B. We need to note that even though B always occurs whenever A occurs it is possible for B to occur without A e.g. good design is sufficient for safe design. Also in the logical implication ‘If A then B’ or ‘A implies B’ A is sufficient for B and B is necessary for A e.g. ‘If (good design) then (safe design)’. 2. In interval probability theory using the Italian flag, sufficiency is a conditional measure of the degree to which success of a sub-process E is required for success of a super-process H i.e. p(H/E). It is the evidence for H given E expressed as an interval probability
sustainability Keeping something going over time – keeping from failing or enduring without giving way. The ability of a development to meet the needs of the present without compromising the ability of future generations to meet theirs. Sustainable engineering requires us to become explicitly aware of certain values such as a) a concern for the needs and right of future generations; b) an appreciation of the importance of diversity – see biodiversity; c) a responsible and precautionary attitude to risk when there are significant ‘don’t knows’ so that the consequences of decisions may, as far as practically possible be reversible; d) achieving a balance between various processes – physical, business social etc. There is a real need to recognise the interdependence of systems and especially between people and the physical world.
synergy Synergy occurs when parts combine to produce a total effect that is greater than the sum of the individual parts.
system An overused word with many meanings and uses. Used loosely it just refers to any group of connected objects. More precisely as used in systems theory it is a complex whole with a set of interacting parts as a connected network or mechanism which has emergent properties that explain why the whole can be more than the sum of its parts. A hard system is a physical one that can be explained in terms of action and reaction. It is always embedded in a soft system involving people with action, reaction and intention. System identification is about deciding what is to be part of the system and what is in the meta-system of context.
systems thinking Systems is not a subject like strength of materials or mathematics, rather it is a way of thinking – a way of tackling problems. There are three important features, holons, connectivity and a new view of process. Thus the systems thinker looks for a hierarchy of interacting processes to build into a process model. Attributes are then attached based on questions to why (purpose), how (method), who, what, where, when (the change parameters).
tame problems Problems which are linear, manageable and controllable. Sometimes refered to as simple problems.
technology There are four different uses of the word. To describe objects (such as a computer), as knowledge (we have the technology), as activity (crafting, inventing) and as an expression of human will (to make).
telegraph Long distance transmission of messages without the exchange of the physical object bearing the message.
transistor A semiconductor device that is a valve or an amplifier
trebuchet A medieval war machine with a sling to hurl missiles
truth The commonplace idea that there is a correspondence between a statement and the facts. But facts are true statements so there is a circular argument that can only be resolved by recognising that truth depends on context.
turbine A rotary engine where a flow of a fluid turns a shaft to drive a machine
uncertainty Absence of precise and complete knowledge. Managing uncertainty is a key issue. Decisions depend on the past experiences and case histories, the present state of affairs through observation and audit and the future through prediction – scientific or otherwise. We try to anticipate unintended consequences and make contingency plans. Unintended consequences can be a benefit as well as a threat. If we are ready to manage them then we can take advantage of the good ones and minimise the disadvantages of the bad ones. Uncertainty consists of fuzziness, incompleteness and randomness.
value 1. The regard, merit, importance or worth given to something. It is the basis for showing a preference i.e. making a choice. The criteria on which our values are based.

2. Material or monetary worth.

3. The magnitude of a mathematical variable e.g. the value of x is 2 or x = 2.

valve A switch or controller of flow
vector A quantity that has both magnitude and direction c.f. scalar
VHF Very High Frequency
vision Ability to articulate what the future will or could be like with imagination and wisdom. The shared vision of a group is their shared mental model of the future they seek to create. It captures their values and expresses their larger sense of purpose. Vision statements are often condemned as having little content. However just like mission statements the value is in the process by which they are developed. If they are written by top management with no consultation then they are ineffective. However if they express the beliefs and collective personal visions they can be extremely effective. Leaders must ‘walk the talk’ to obtain commitment. Such belief is created by actions not words. Effective teams and organisations have a clear sense of purpose expressed through vision, mission, aims and objectives.
vulnerability A property of a system where small damage can cause disproportionate consequences e.g. Ronan Point high rise block of flats in London in 1968 was a vulnerable structure because a small domestic gas explosion in one flat or apartment, caused the whole side of the building to collapse. Vulnerability also concerns low chance – high consequence risks. The theory of vulnerability is underdeveloped and needs much more attention for all complex systems from computer networks to engineering structures.
watts A unit of power equal to one joule per second
wicked problem Problems and situations that do not seem to yield to easy solutions – contrasted with tame problems c.f. messy problems. There seem to be so many interlocking issues and constraints that you don’t seem to understand the problem until you have developed a solution. There are so many people involved it seems more like a social process. The constraints change over time and the goal posts shift.
work Exertion or effort and equal to one Newton being moved one metre or one Joule
worldview The way we look at the world, our point of view. We attribute meaning to things by interpreting it in the light of our education and experience. Thus the same issue will be formulated as an economic problem by an economist, an engineering problem by an engineer, a political problem by a politician etc.