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In zoology, the word "form" or forma (literally Latin for form) is a strictly informal term that is sometimes used to describe organisms. Under the International Code of Zoological Nomenclature the term has no standing (it is not accepted). In other words, although form names are Latin, and are sometimes wrongly appended to a binomial name, in a zoological context, forms have no taxonomic significance at all.

Usage of the term

Some zoologists use the word "form" or "forma" to describe variation in animals, especially insects, as part of a series of terms and abbreviations that are appended to the binomen or trinomen. Many 'typical specimens' may be described, but none should be considered absolute, unconditional or categorical. Forms have no official status, though they are sometimes useful in describing altitudinal or geographical clines. As opposed to morphs (see below), a subpopulation usually consists of a single form only at any given point of time.

forma geographica - f. geogr.

forma localis - f. loc.

forma alta - f. alt.

forma vernalis - f. vern. (spring form) forma aestivalis - f. aest. (summer form) forma autumnalis - f. autumn. (autumn form)

aberratio - ab.


  • A morph is a similar concept with a less restricted occurrence (see also Polymorphism). As neither forms nor morphs are officially recognised terminology in zoology, application can vary but, generally, morphs occur without geographical or seasonal restriction, and may constitute a significant part of the population; usually, several morphs co-occur in a single subpopulation at a given time. The peppered moth is a famous example.
  • Botanical nomenclature is much more complex, with the use of varieties, subvarieties, and forms being formally regulated by the ICBN.

See also

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