longus

Longus is a Latin adjective meaning long. In scientific terminology, it is used as a descriptive epithet in the naming of organisms and anatomical structures to indicate an elongated form, often contrasting with brevis (short). The form longus is masculine; longa is feminine; longum is neuter, and the word agrees with the gender, number, and case of the noun it modifies.

In anatomy, longus denotes relatively long muscles or structures. Common examples include extensor digitorum longus and flexor digitorum longus, both muscles of the lower leg that affect toe movement. The fibularis longus (peroneus longus) is another long muscle running along the lateral aspect of the leg. In the neck region, muscles such as longus capitis and longus coli are named for their length and deep position relative to surrounding tissues.

In taxonomy, longus appears as a species epithet across various genera to indicate an elongated feature of the organism, spanning plants and animals. This reflects a broader Latin descriptive convention used in biological naming.

The term forms part of a family of Latin descriptors used in scientific nomenclature, alongside brevis (short) and other length-related terms, and it remains in contemporary medical and biological usage.