The glossary of Systems Thinking terms and concepts shown on this page is based on a document originally developed in 2016 by Gilbert, Gross, and Kreutz for the InTeGrate platform. Lisa Gilbert created a modified newer version in conjunction with David Laviska and the American Chemical Society Green Chemistry Institute in 2024. The document provided below has been further edited and expanded by Alisha Szozda and Jane Wissinger for posting here on the SaSTICE website.
The list of terms and concepts is restricted to what the authors determined the most essential entries, and the definitions/explanations provided are intentionally brief. More information can be found at the following additional sources:
A balancing feedback loop diminishes the effect of disturbances. It works to balance flux between two or more components and moves a system toward equilibrium.
A boundary shows the limit or edge of a closed system; a boundary separates a system and the surrounding environment.
A box model is a graphical and quantitative representation of a system, where components and fluxes are given values and followed through time.
Causation describes how a change in one component of a system affects another. A “causal loop” is similar to a “feedback loop” and represents relationships between components of a system.
See Forcing
Closed/Open System
These terms describe whether matter and/or energy are contained within a system (closed) or potentially exchanged across a boundary between a system (open) and its environment.
Component
A component is an individual part of a system; it can be a reservoir, an attribute of a system, or a subsystem.
Converter
See Flux
Couplings are links between system components; they can be either positive (a change in one component causes a change in the same direction in the linked component) or negative (change in one component stimulates a change of the opposite direction in the linked component).
A cycle represents constant movement of material from one component to another.
A disturbance represents an applied change (e.g., increase or decrease) to one or more components of a system.
See Forcing
Dynamic behavior describes how a system, or component of a system, acts over time based on circular, interconnected cause/effect relationships.
See Box Model
See Response
Emergent properties arise from the interactive behavior of a system as a whole and represent the cumulative product of the actions and interactions of the collective components of a system. Emergent properties may or may not be predictable from the individual properties of system components.
Environment represents all the components of the surroundings in which a system is located. The environment exists outside system boundaries.
Systems in a state of stable equilibrium tend to reestablish equilibrium after experiencing disturbances. In this case, disturbances from equilibrium will be followed by system responses (including negative feedback loops) that return the system to its equilibrium state. This is also called “homeostasis” or “dynamic equilibrium”. Systems with an unstable state of equilibrium respond to disturbances with positive feedback loops and move further from equilibrium.
Feedback represents a self-perpetuating mechanism of change and subsequent response(s) to that change.
See Flux
Flux and flow are quantitative terms that describe rate of matter or energy movement (amount per unit time) to or from a system component.
Forcing is a persistent disturbance of a system.
Flux into a system component.
Leverage Point
A leverage point represents a component of a system that can be targeted for disturbance (by external forces/actors) to achieve a desired or predicted outcome.
Negative Feedback Loop
See Balancing Feedback Loop
Open/Closed System
These terms describe whether matter and/or energy are contained within a system (closed) or potentially exchanged across a boundary between a system (open) and its environment.
Output
Flux out of a system component.
Perturbation
A temporary disturbance of a system.
Pool
See Reservoir
Positive Feedback Loop
See Reinforcing Feedback Loop
Reductionism
Reductionism can be thought of as the opposite of systems thinking. It is an approach to understanding complex systems that involves breaking down a system into its individual components and assessing them as isolated entities, separate from the system to which they belong.
Reinforcing Feedback Loop
Amplifies the effect of disturbances, moves system away from equilibrium
Reservoir
A system component that contains matter or energy.
Residence Time
The average length of time a matter or energy remains in a given reservoir
Response
A response denotes the change in a system resulting from a disturbance, perturbation, or forcing.
Sink
If the flux of matter or energy into a component is greater than the flux out of the component, then that component is defined as a sink.
SOCME
Acronym for Systems-Oriented Concept Map Extension, a type of diagram used to represent a system.
Source
If the flux of matter or energy out of a reservoir is greater than the flux into the reservoir, then that reservoir is defined as a source.
Steady State
A system is at steady state when there is no change in any component or source/sink in that system measured as a function of time. (Note: A system at steady state is not necessarily in a state of equilibrium.)
Stock
See Reservoir
See Box Model
Storage
See Reservoir
System
A system is an entity composed of diverse but interrelated parts or components that function as a complex whole.
Systems Diagram/Map
A systems diagram or map is a graphical representation of a system, showing system components and couplings.
Systems Thinking
Systems thinking can be thought of as the opposite of reductionism. It is a holistic approach to understanding complex systems that involves acknowledging the intricacies of connections, counterbalances, and synergies between system components and thinking broadly about context, related systems/subsystems, flows into/out of the system, and the surrounding environment. A systems thinking approach recognizes that individual components of a system cannot be isolated without affecting the properties of the system as a whole.
Threshold
A threshold is the level or value at which a rapid change in the system state, often from one equilibrium state to another, occurs.
Tipping Point
See Threshold
Transfer
See Flux
A vicious cycle is a reinforcing Feedback Loop with an emerging harmful or negative result: two or more components of a system act to intensify each other and lead to a worsening situation.
Virtuous Cycle
A virtuous cycle is a reinforcing Feedback Loop with an emerging helpful or positive result: two or more components of a system act to intensify each other and lead to an improving situation.