polymorphism, of minerals, property of crystallizing in two or more distinct forms. Calcium carbonate is dimorphous (two forms), crystallizing as calcite or aragonite. Titanium dioxide is trimorphous; its three forms are brookite, anatase (or octahedrite), and rutile. Polymorphism of an element is called allotropy. The process was discovered (1821) by Eilhard Mitscherlich. See isomorphism; mineral; crystal.

Discontinuous genetic variation that results in the occurrence of several different forms or types of individuals among the members of a single species. The most obvious example of polymorphism is the separation of most higher organisms into male and female sexes. Another example is the different blood types in humans. A polymorphism that persists over many generations is usually maintained because no one form has an overall advantage or disadvantage over the others in terms of natural selection. Some polymorphisms have no visible manifestations. The castes that occur in social insects are a special form of polymorphism that results from differences in nutrition rather than from genetic variation.

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In general, polymorphism describes multiple possible states for a single property (it is said to be polymorphic, or polymorphous).

Polymorphism may specifically refer to:In the biological sciences

• Polymorphism (biology), having multiple alleles of a gene within a population, usually expressing different phenotypes
• Polymorphism (biophysics) also referred to as Lipid polymorphism, the property of amphiphiles that gives rise to various aggregations of lipids
• Polymorphism (botany), the ability of a plant to produce both quiescent and dormant seeds
• In sexology, polymorphous perversityIn computing:
• Type polymorphism, allowing program code to work with various types
• Polymorphism in object-oriented programming
• Polymorphic code, self-modifying program code designed to defeat anti-virus programsMiscellany:
• Polymorphism (materials science), the ability of a solid material to exist in more than one form or crystal structure

See also

• Dimorphism
• Polymorph