Biology. the theory that an embryo develops from the successive differentiation of an originally undifferentiated structure (opposed to preformation ).
Genetics. the approximately stepwise process by which genetic information is modified and translated into the substance and behavior of an organism. See also epigenetics.
Geology. ore deposition subsequent to the original formation of the enclosing country rock.

1800–10; epi- + -genesis

epigenesist, epigenist [ih-pij-uh-nist] , noun
epigenetic [ep-i-juh-net-ik] , adjective
epigenetically, adverb
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World English Dictionary
epigenesis (ˌɛpɪˈdʒɛnɪsɪs)
1.  Compare preformation the widely accepted theory that an individual animal or plant develops by the gradual differentiation and elaboration of a fertilized egg cell
2.  the formation or alteration of rocks after the surrounding rock has been formed
3.  alteration of the mineral composition of a rock by external agents: a type of metamorphism

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American Heritage
Medical Dictionary

epigenesis ep·i·gen·e·sis (ěp'ə-jěn'ĭ-sĭs)
The theory that an individual is developed by successive differentiation of an unstructured egg rather than by a simple enlarging of a preformed entity.

ep'i·ge·net'ic (-jə-nět'ĭk) adj.
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Example sentences
Epigenesis may even account for differences between species.
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