Merriam-Webster Collegiate Dictionary - exogenous

 adjective  Etymology: French exogene ~, from exo- + -gene (from Greek -genes born) — more at -gen  Date: 1830  1. produced by growth from superficial tissue ~ roots produced by leaves  2.  a. caused by factors (as food or a traumatic factor) or an agent (as a disease-producing organism) from outside the organism or system ~ obesity ~ psychic depression ~ market fluctuations  b. introduced from or produced outside the organism or system; specifically not synthesized within the organism or system  • ~ly adverb