Exogenous (or exogeneous) (from the Greek words "exo"
and "gen", meaning "outside" and "production") refers to an action
or object coming from outside a system. It is the opposite of
endogenous, something generated from
within the system.
In an economicmodel, an exogenous change
is one that comes from outside the model and is unexplained by the
model. For example, in the simple supply and demand model, a change in
consumer tastes or preferences is unexplained by the model and also
leads to endogenous changes in demand that lead to
changes in the equilibrium price. Put another
way, an exogenous change involves an alteration of a variable that
is autonomous, i.e., unaffected by the workings of the model.
In linear regression, it means that the
variable is independent of all other response values.
In biology, "exogenous"
refers to an action or object coming from the outside of a system.
For example, an exogenous contrast agent in medical imaging refers
to a liquid injected into the patient intravenously that
enhances visibility of a pathology, such as a tumor.
In biology, an exogenous
factor is any material that is present and active in an individual
organism or living cell but that
originated outside of that organism, as opposed to an endogenous
In Ludology, the study of games, exogenous
refers to anything outside the game itself. Therefore an item in a
Massive Multiplayer Online Game would have exogenous value if
people were buying it with real world money rather than in game
currency (though its in game cost would be endogenous).