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System Dynamics Glossary

accumulation (integration)

a gradual, non-instantaneous increase or decrease of a quantity over time. An accumulator is also referred to as a stock or level and represents the state of a system. To accumulate is the act of increasing and decreasing the size of a state variable (a stock) over time.


the grouping of numerous distinct system components into one variable. Aggregation is done for simplicity when the grouping generates the same behavior of interest as those generated by the components separately

aggregation level

the extent to which the system components are aggregated
or disaggregated.

aging chain

a sequence of stocks connected by conserved ows in which
the stocks depict the contents of the chain in different stages, conditions or locations, and the contents move in one direction along the aging chain.

“A System Dynamics Glossary” has been compiled by David Ford and published in System Dynamics Review.  It is provided free for all to use if proper citation is given. 

System Dynamics Review vol 35, No 4 (October/December 2019): 369379
Published online in Wiley Online Library
( DOI: 10.1002/sdr.1641