In a variety of contexts, exogeny or exogeneity (from Greek exo, meaning "outside", and gignomai, meaning "to produce") is the fact of an action or object originating externally. It contrasts withendogeny or endogeneity, the fact of being influenced within a system.
Exogeny is a noun referring to something being influenced by or coming from "outside" (i.e., externally). In the context of biology, exogenous, usually refers to forces or products originating from outside a living organism or its cells. It is an antonym to endogeny.