Efficiens

Efficiens is a Latin adjective meaning "efficient" or "effective." It derives from the verb efficere, meaning to bring about or accomplish, with efficiens functioning as a present active participle, roughly translating to "the one who brings about" or simply "efficient." In scientific and scholarly usage, efficiens may appear as a descriptive epithet in Latin-based taxonomic names, where adjectives agree in gender and number with the genus. Its use signals a trait such as efficiency of metabolism, production, or growth, though it is not among the most common taxonomic epithets.

Beyond taxonomy, the term occurs in Latin phrases within philosophy and theology. In Aristotelian and Scholastic contexts, the phrase causa efficiens denotes the efficient cause—the agent or source responsible for bringing something into being, as distinct from the material, formal, or final causes.

In modern writing, efficiens is primarily encountered in Latinized scientific or philosophical terms rather than as a standalone term in everyday language. When used in taxonomic names, it is typically treated as a lowercase adjective and must harmonize with the corresponding genus name.

See also: causa efficiens, efficiency, etymology of Latin scientific names.