[pol-ee-mawr-fiz-uh m]


the state or condition of being polymorphous.
Crystallography. crystallization into two or more chemically identical but crystallographically distinct forms.
Biology. the existence of an organism in several form or color varieties.
Genetics. the presence of two or more distinct phenotypes in a population due to the expression of different alleles of a given gene, as human blood groups O, A, B, and AB.

Origin of polymorphism

First recorded in 1830–40; polymorph + -ism
Related formspol·y·mor·phis·tic, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for polymorphism

Historical Examples of polymorphism

  • It illustrates the phenomena of polymorphism most beautifully.

    The Butterfly Book

    William Jacob Holland

  • Spencer, Herbert, controversy with Weismann on polymorphism in insects, 125.

  • Polymorphism was first observed by Mitscherlich in the case of sodium phosphate, and later in the case of sulphur.

  • The horse-radish (Cochlearia Armoracia) may also be instanced as a common illustration of polymorphism in the leaves.

    Vegetable Teratology

    Maxwell T. Masters

  • Here, then, is a colony in which the division of labour has reached a remarkable degree of polymorphism.

British Dictionary definitions for polymorphism



  1. the occurrence of more than one form of individual in a single species within an interbreeding population
  2. the occurrence of more than one form in the individual polyps of a coelenterate colony
the existence or formation of different types of crystal of the same chemical compound
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 polymorphism

1839, from polymorph + -ism.

Online Etymology Dictionary, © 2010 Douglas Harper

polymorphism in Medicine




The occurrence of different forms, stages, or types in individual organisms or in organisms of the same species, independent of sexual variations.
Crystallization of a compound in at least two distinct forms.pleomorphism
Related formspol′y•morphic null adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

polymorphism in Science



The occurrence of more than one form, as several alleles of a particular gene or winged and wingless forms of the same species. In bees, the presence of queen, worker, and drone is an example of polymorphism. Differences between the sexes and between breeds of domesticated animals are not considered examples of polymorphism.
The crystallization of a compound in at least two distinct forms. Diamond and graphite, for example, are polymorphs of the element carbon. They both consist entirely of carbon but have different crystal structures and different physical properties.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.