In zoology, form (Latin: forma) 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 do not have any taxonomic significance; such names are unavailable, do not have authors or dates, and do not compete for homonymy.

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.

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