[ep-uh-fuh-nom-uh-non, -nuh n]
noun, plural ep·i·phe·nom·e·na [ep-uh-fuh-nom-uh-nuh] /ˌɛp ə fəˈnɒm ə nə/, ep·i·phe·nom·e·nons.
  1. Pathology. a secondary or additional symptom or complication arising during the course of a disease.
  2. any secondary phenomenon.

Origin of epiphenomenon

First recorded in 1700–10; epi- + phenomenon
Related formsep·i·phe·nom·e·nal, adjectiveep·i·phe·nom·e·nal·ly, adverb
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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Historical Examples of epiphenomenon

British Dictionary definitions for epiphenomenon


noun plural -na (-nə)
  1. a secondary or additional phenomenon; by-product
  2. pathol an unexpected or atypical symptom or occurrence during the course of a disease
Derived Formsepiphenomenal, adjectiveepiphenomenally, adverb
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for epiphenomenon

1706, "secondary symptom," from epi- + phenomenon. Plural is epiphenomena. Related: Epiphenomenal.

Online Etymology Dictionary, © 2010 Douglas Harper

epiphenomenon in Medicine


  1. An additional condition or symptom in the course of a disease, not necessarily connected with the disease.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.