In a variety of contexts, exogeny or exogeneity (from Greek, Modern exo, meaning 'outside', and gignomai, meaning 'to produce') is the fact of an action or object originating externally. It contrasts with endogeny or endogeneity, the fact of being influenced within a system.

  • In an economic model, an exogenous change is one that comes from outside the model and is unexplained by the model.
  • In linear regression, an exogenous variable is independent of the random error term in the linear model.
  • In biology, an exogenous contrast agent in medical imaging for example, is a liquid injected into the patient intravenously that enhances visibility of a pathology, such as a tumor. An exogenous factor is any material that is present and active in an individual organism or living cell but that originated outside that organism, as opposed to an endogenous factor.
  • In geography, exogenous processes all take place outside the Earth and all the other planets. Weathering, erosion, transportation and sedimentation are the main exogenous processes.
  • In attentional psychology, exogenous stimuli are external stimuli without conscious intention.[1] An example of this is attention drawn to a flashing light in the periphery of vision.
  • In ludology, the study of games, an exogenous item is anything outside the game itself. Therefore, an item in a massively 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).
  • In materials science, an exogenous property of a substance is derived from outside or external influences, such as a nano-doped material.
  • In philosophy, the origins of existence of self, or the identity of self, emanating from, or sustaining, outside the natural or influenced realm, is exogenous.

See also


  1. ^ Posner, M.I. (1980), Orienting of attention. Quarterly Journal of Experimental Psychology, 32: 3–25.

External links

  • The dictionary definition of exogeny at Wiktionary
Endogeny (biology)

Endogenous substances and processes are those that originate from within a system such as an organism, tissue, or cell. The term is chiefly used in biology but also in other fields.Endogenous substances and processes contrast with exogenous ones, such as drugs, which originate from outside of the organism.


Exogen has several meanings:

an archaic term meaning a woody plant whose stem is formed by successive accretions to the outside of the wood under the bark; this group is essentially the dicots.

a phase in the life cycle of a hair follicle in which a hair exits the follicle.

a non-invasive ultrasound bone healing medical device, that aids in bone healing manufactured by Bioventus.

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