Polymorphism

Polymorphism is the occurrence of two or more distinct forms of a trait, substance, or structure within a given system. The term comes from Greek roots meaning many shapes. It is used in several disciplines to describe diversity that arises from different underlying mechanisms.

In biology, genetic polymorphism refers to the presence of multiple alleles at a gene locus in a population at appreciable frequencies. This variation can be matched by different phenotypes, colors, or biochemical traits. Balanced polymorphism occurs when natural selection favors maintaining multiple alleles, such as through heterozygote advantage or changing environments. Classic examples include the ABO blood group system and the sickle cell trait, where different forms persist because they provide survival benefits in particular contexts. Polymorphism is a property of populations rather than individuals and can influence evolution, adaptation, and speciation.

In chemistry and mineralogy, polymorphism describes a single chemical substance that can crystallize into more than one distinct crystal structure or phase. Different polymorphs have different physical properties, such as hardness, density, or solubility. Common examples include carbon’s diamond and graphite forms, or silica’s quartz and cristobalite. Polymorphism is important in materials science, pharmaceuticals, and geology, since transitions between polymorphs can affect stability, manufacturability, and performance.

In computer science, polymorphism denotes the ability of code to work with objects of different types through a common interface. It encompasses subtyping (inheritance-based polymorphism), where methods can be overridden; parametric polymorphism (generics), which allows code to operate on various data types; and ad hoc polymorphism (overloading), where the same operation behaves differently for different types. Polymorphism enables flexible, extensible software design.