interna

Interna is a term of Latin origin used across disciplines to denote internal or inner parts. Grammatically, interna is the feminine singular form of internus, and in many contexts it functions as part of compound terms or as a noun meaning “the internal parts.” In modern scientific writing, it largely appears in fixed phrases rather than as a standalone term and is often contrasted with externa to distinguish inner from outer components.

In anatomy and medicine, interna commonly occurs in expressions for inner layers or membranes of tubular structures, for example tunica interna or membrana interna, indicating the inner coat or lining. In vascular biology and other fields with classical terminology, similar pairings with externa describe inner versus outer layers. These usages persist in historical texts and in some contemporary contexts that retain traditional Latin nomenclature.

In other fields, interna may appear in botanical or zoological contexts to denote internal tissues or compartments, typically within longer compound terms. In modern Romance languages, interna functions as a lexical form meaning “internal” (for example italiana interna, española interna, portuguesa interna); as a noun it is less common and its precise meaning depends on the context and tradition of the text.

See also: externa, intima, tunica interna, membrana interna.