Table 1 Glossary of system definitions^a

Adaptation

Adjustments in the behaviour of a system or programme in response to new conditions.

Boundary (system boundary)

System boundaries define what components of a system need to be included, or can be excluded, to understand the system under study.

Causal loop diagram (CLD)

Visual representation of a system consisting of closed loops of causal influences that capture how components of a system interrelate.

Complex adaptive system

A system is a set of individual components that are interconnected. A complex adaptive system is more than the sum of its parts: the system as a whole has different properties to those that can be found in individual components of the system.

Disruption

A significant event that prevents a system from continuing its normal trajectory or behaviour.

Dynamic

A complex adaptive system is dynamic – the behaviour of the system changes over time.

Emergence

Properties of a complex system that cannot be directly predicted from the elements within it and are more than just the sum of its parts.

Feedback loop

Feedback occurs when the output of a causal influence also serves as an input of that causal influence. A feedback loop is a sequence of components and interconnections that creates a closed loop of causal influences.

Group model building (GMB)

Methodology for developing models in which people as a group participate actively and simultaneously in building a causal loop diagram.

Leverage points

Places in a system where a small change could lead to a large change in the system’s behaviour.

Non-linear relationship

Relationship between two components in a system, in which a change in the first component (‘independent variable’) does not produce a proportional effect in the second component (‘dependent variable’).

Self-organisation

The ability of a complex adaptive system to structure itself, to create a new structure, to learn, or to diversify by local interactions between individual components, rather than by external forces.

Social network analysis (SNA)

Technique used to describe and analyse patterns of social interaction between different entities (e.g. people, organisations).

System behaviour

Individual components in complex adaptive systems are interconnected in such a way that they together produce a distinct pattern of behaviour over time. The system’s function or purpose is what ultimately determines how the system as a whole will behave.

System dynamics

In system dynamics, models (e.g. causal loop diagrams) are built that represent the dynamic complexity of high-level phenomena.

Systems thinking

A way of conceptualising and making sense of the world through the application of systems concepts such as adaptation, feedback loops and emergence.

Uncertainty

Under conditions of complexity, processes and outcomes cannot be predicted, be controlled or be known in advance.

Unintended consequences

Unplanned (and typically undesirable) side-effects of actions in a system, often occurring after a time delay.