falsus

Falsus is a Latin adjective and a Latin participle form meaning false, deceitful, or dishonest. In Latin grammar, falsus is the masculine singular perfect passive participle of fallere, with femenina falsa and neutrum falsum forming the other gender and number forms. The term carries connotations of deception and unreliability and appears in scholarly Latin as well as in translated passages.

In legal and rhetorical contexts, falsus is most widely recognized through the maxim falsus in uno, falsus in omnibus, meaning “false in one thing, false in everything.” The maxim has been used to evaluate the credibility of witnesses or testimony, suggesting that a false statement about a material matter undermines overall reliability. Modern evidence law, however, often treats credibility with nuance, distinguishing specific misstatements from general trustworthiness.

Beyond law, falsus appears in classical and medieval writings to describe lies, falsehoods, or deceptive appearances. In translations and scholarly discussions, the term is used to discuss truth, perception, and epistemology, sometimes illustrating arguments about reliability and deception.

In taxonomy and biology, Latin participles commonly appear in species names, and falsus may occur as part of a binomial epithet to signal disputed or mistaken characteristics in historical naming, though it is not a standardized taxonomic label by itself.

See also: fallere, falsum, falsa, falsity, falsification.