Mentalis

Part of speech: noun, adjective

Definitions

1. A term referring to the mental aspects of psychology or philosophy
2. relating to the mind's internal processes or functions
3. used as an adjective to describe anything associated with cognitive faculties

Etymology: The word has nothing to do with the mind despite its meaning. In English it is a technical anatomical term, borrowed from New Latin "mentalis," which was shortened from the phrase "musculus mentalis," meaning "the chin muscle." The chin is the "mentum" in Latin, and the adjective "mentalis" was simply the name for anything belonging to that part of the face. Anatomists used the full phrase for the small muscle that pulls the lower lip up and wrinkles the chin, and over time the noun was dropped, leaving the adjective to stand alone as the label for the muscle. That leaves a neat twist: the English meaning "of the mind" is a coincidence of form. "Mental" in the sense of the mind comes from a different Latin root, "mens," so the two words look alike while sharing no history. Readers meeting "mentalis" in a textbook are therefore looking at a chin, not a thought.