invariabilis

Invariabilis is a Latin adjective meaning unchanging, invariable, or constant. In biological nomenclature, invariabilis is commonly used as a specific or subspecific epithet in combination with a genus name to form a species or subspecies designation.

Grammatical form and usage: invariabilis is the masculine and feminine nominative singular form of the adjective; the neuter nominative singular is invariabile. It must agree in gender with the genus. Like other Latin epithets, it is not capitalized in binomial or trinomial names.

Taxonomic significance: The epithet invariabilis often signals that the author described a trait as constant or characterizing a taxon across observed specimens. However, the choice of epithet is historical and descriptive rather than a guarantee of absolute invariance; later research can reveal variation within the taxon. The use of invariabilis is thus descriptive rather than prescriptive about variability.

Scope of use: As a descriptive Latin epithet, invariabilis appears across zoological, botanical, and microbiological names. It is one of many adjectives derived from Latin that convey a particular trait or impression about the taxon being named. Its application follows the standard rules of the International Code of Zoological Nomenclature and the International Code of Nomenclature for algae, fungi, and plants.

See also: Latin nomenclature, binomial nomenclature, taxonomic epithets, Latin grammar in taxonomy.