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System Dynamics Glossary

This is the System Dynamics Glossary compiled by David N. Ford and Accepted by Yaman Barlas. It was published on November 7th 2019 here: https://doi.org/10.1002/sdr.1641.

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Introduction

As a narrowly focused dictionary, this glossary defines commonly used terms that are central to traditional system dynamics and some more general terms that have special meanings or particular importance within system dynamics. General terms that have no special meanings in system dynamics, application‐specific terms, and software‐specific terms are not included. The reader is referred to the relevant literature for those definitions, as well as detailed descriptions, explanations, and examples of the terms included here.

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Click on the Concept to View the complete Description.

Concept
Description
Half‐life
The time required for a stock to move halfway towards its goal. Associated with goal‐seeking behavior. The half‐life is the converse of doubling time in positive feedback.
High‐leverage point (high‐leverage parameter)
Part of a system where small changes can have a very large impact on system behavior and is therefore effective for focusing system design, management attention and resources.
Homeostasis
The tendency of organisms to preserve their equilibrium conditions. Control through the operation of negative feedback loops—homeostasis is reached when the goal is attained and stable equilibrium achieved.
Impulse
Theoretically, a signal of zero duration but non‐zero finite height and area. Practically, in simulation models, a signal (flow) of specified area lasting for one solution interval and occurring at a specified time.
Information delay
A delay that represents the gradual adjustment of information, perceptions or beliefs, or a gradually delayed impact of some variable on a flow or auxiliary variable. Used to model non‐conserved variables.
Integration
See accumulation.
Integration error
Error generated in computer simulations due to the mathematical method used to approximately compute variable values.
Limits to growth
A resource constraint, an external or internal limiting response to growth. An initial growth begins to slow and eventually comes to a halt at the limit, and may even reverse itself and collapse.
Linear system
A system in which all relations between variables are mathematically linear. In such systems, the complete behavior can be found by superimposing different behavior modes without interacting with one another.
Link polarity
See causal link polarity.
Little's law
The relationship among the size of a stock, the net flow into or out of the stock, and the average time material stays in the stock under conditions of perfect mixing and when the system is in equilibrium. At equilibrium, the size of the stock is the product of the net flow and the delay.
Look‐up function
See table function.

References

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