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[pol-ee-mawr-fiz-uh m] /ˌpɒl iˈmɔr fɪz əm/
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
1830-40; polymorph + -ism
Related forms
polymorphistic, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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Examples from the Web for polymorphism
Historical Examples
  • It illustrates the phenomena of polymorphism most beautifully.

    The Butterfly Book William Jacob Holland
  • Here, then, is a colony in which the division of labour has reached a remarkable degree of polymorphism.

    The Industries of Animals Frdric Houssay
  • Spencer, Herbert, controversy with Weismann on polymorphism in insects, 125.

  • By suitable combinations of eosin and cherry most of the cases of polymorphism in butterflies may be simulated.

  • It is chiefly amongst the microscopic species that polymorphism has been determined.

    Fungi: Their Nature and Uses Mordecai Cubitt Cooke
  • I believe it will be found that a considerable number of what have been classed as varieties are really cases of polymorphism.

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

    Vegetable Teratology Maxwell T. Masters
  • The tendency of the female to dimorphism and polymorphism has been of great importance in determining this predominance.

    Darwin and Modern Science A.C. Seward and Others
  • We have adduced in the foregoing pages a few instances which will serve to illustrate the polymorphism of fungi.

    Fungi: Their Nature and Uses Mordecai Cubitt Cooke
  • We now understand the process by which a polymorphic race maintains its 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
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Word Origin and History for polymorphism

1839, from polymorph + -ism.

Online Etymology Dictionary, © 2010 Douglas Harper
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polymorphism in Medicine

polymorphism pol·y·mor·phism (pŏl'ē-môr'fĭz'əm)

  1. The occurrence of different forms, stages, or types in individual organisms or in organisms of the same species, independent of sexual variations.

  2. Crystallization of a compound in at least two distinct forms. Also called pleomorphism.

pol'y·mor'phic or pol'y·mor'phous adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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polymorphism in Science
  1. The existence of two or more different forms in an adult organism of the same species, as of an insect. 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.

  2. 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 © 2002. Published by Houghton Mifflin. All rights reserved.
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polymorphism in Technology

theory, programming
A concept first identified by Christopher Strachey (1967) and developed by Hindley and Milner, allowing types such as list of anything. E.g. in Haskell:
length :: [a] -> Int
is a function which operates on a list of objects of any type, a (a is a type variable). This is known as parametric polymorphism. Polymorphic typing allows strong type checking as well as generic functions. ML in 1976 was the first language with polymorphic typing.
Ad-hoc polymorphism (better described as overloading) is the ability to use the same syntax for objects of different types, e.g. "+" for addition of reals and integers or "-" for unary negation or diadic subtraction. Parametric polymorphism allows the same object code for a function to handle arguments of many types but overloading only reuses syntax and requires different code to handle different types.
See also generic type variable.
In object-oriented programming, the term is used to describe a variable that may refer to objects whose class is not known at compile time and which respond at run time according to the actual class of the object to which they refer.

The Free On-line Dictionary of Computing, © Denis Howe 2010
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