aptus

Aptus is a Latin adjective meaning fit, suitable, or proper. It is used to describe something or someone that is appropriate to a particular purpose, circumstance, or context. In Latin, aptus agrees in gender and number with the noun it modifies, with forms such as aptus (masculine singular), apta (feminine singular), aptum (neuter singular), and apti, aptae, apta (plural).

In classical Latin, aptus appears in phrases that convey suitability or propriety, for example id aptum est, meaning “that is fitting.” The adjective can modify a wide range of nouns, including people, objects, actions, or situations, to indicate appropriateness or fitness.

Aptus has given rise to several English derivatives through the Latin and French routes. The English word apt derives from Old French apte, itself from Latin aptus. The noun aptitude comes from Latin aptitudo, meaning “fitness” or “ability.” The verb adapt comes from Latin adaptare (to fit to), formed with ad- (toward) and aptare (to fit). The negative form inaptus occurs in Latin and has been carried into English as inapt, meaning not suitable or inappropriate.

Beyond its lexical role, aptus is mainly of interest in linguistic and etymological discussions as a classic example of how Latin adjectives influence modern vocabularies and how the concept of suitability persists across languages. See also words such as apt, aptitude, adapt, and inapt.