In zoology the term forma (literally Latin for form) is an informal term; under the International Code of Zoological Nomenclature

International Code of Zoological Nomenclature

The International Code of Zoological Nomenclature is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals...

it has no standing (it is not accepted).

By some zoologists it is used to describe variation in animals, especially insect

Insect

Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s, as part of a series of terms and abbreviations that are appended to the binomen

Binomen

In zoological nomenclature, a binomen , is the two-part name of a species. The term was introduced in 1953, abolishing the previously used "binomial name" . A binomen consists of a generic name and a specific epithet...

 or trinomen

Trinomen

In zoological nomenclature, a trinomen , or trinominal name, refers to the name of a subspecies.A trinomen is a name consisting of three names: generic name, specific name and subspecific name. The first two parts alone form the binomen or species name. All three names are typeset in italics, and...

. Many 'typical specimens' may be described, but none should be considered absolute, unconditional or categorical. Forms have no official status, though they may be useful in describing altitudinal or geographical cline

Cline (population genetics)

In biology, an ecocline or simply cline describes an ecotone in which a series of biocommunities display continuous gradient...

s. 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.

If used, nowadays usually denotes a part of a cline; for example for intergrades between subspecies

Subspecies

Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

 in their area of contact.

forma localis - f. loc.

As "f. geogr." but only local, more restricted in occurrence. See also small population size

Small population size

Small populations behave differently from larger populations. They often result in population bottlenecks, which have harmful consequences for the survival of that population.-Demographic effects:...

.

forma alta - f. alt.

Altitudinal features are not necessarily inherited, but may entirely be due to environment. The same applies to temperature or humidity-generated forms, such as:

forma vernalis - f. vern. (spring form)

forma aestivalis - f. aest. (summer form)

forma autumnalis - f. autumn. (autumn form)

aberratio - ab.

May be used for a single individual, for a small group such as an individual and its offspring, or for atypical individuals (for example, albinos).

Also used for commonly observed forms of a species, but in this case use of forma (f.) or morpha, accompanied by a descriptive name, is more conventional.

Notes:

• A morph is a similar concept with a less restricted occurrence (see also Polymorphism
  Polymorphism (biology)
  Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
  
  ). 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
  Peppered moth
  The peppered moth is a temperate species of night-flying moth. Peppered moth evolution is often used by educators as an example of natural selection.- Distribution :...
  
   is a famous example.
• Botanical nomenclature
  Botanical nomenclature
  Botanical nomenclature is the formal, scientific naming of plants. It is related to, but distinct from taxonomy. Plant taxonomy is concerned with grouping and classifying plants; botanical nomenclature then provides names for the results of this process. The starting point for modern botanical...
  
   is much more complex, with the use of varieties, subvarieties
  Subvariety
  In botanical nomenclature, a subvariety is a taxonomic rank below that of variety but above that of form : it is an infraspecific taxon. Its name consists of three parts: a genus name, a specific epithet and an infraspecific epithet. To indicate the rank, the abbreviation "subvar." should be put...
  
  , and forms
  Form (botany)
  In botanical nomenclature, a form is one of the "secondary" taxonomic ranks, below that of variety, which in turn is below that of species; it is an infraspecific taxon...
  
   being formally regulated by the ICBN.