early 15c., "in, of, or pertaining to the mind; characteristic of the intellect," from Late Latin mentalis "of the mind," from Latin mens (genitive mentis) "mind," from PIE root *men- (1) "to think."

In Middle English, also "of the soul, spiritual." From 1520s as "done or performed in the mind." Meaning "crazy, deranged" is by 1927, probably from combinations such as mental patient (1859); mental hospital (1891). Mental health is attested by 1803; mental illness by 1819; mental retardation by 1904.

early 15c., "intellectually, in the mind," from mental + -ly (2). In Middle English also "spiritually, in the soul."

1690s, "mental action or power," from mental (adj.) + -ity. The sense of "intellectual activity" is by 1856; that of "mental character or disposition" is by 1895.

1782, "one devoted to mental pleasures," from mental + -ist. Originally in reference to artistic taste; philosophical sense "one who believes matter in ultimate analysis is a mode of mind or consciousness" (from mentalism) is from 1900. Related: Mentalistic.

Proto-Indo-European root meaning "to think," with derivatives referring to qualities and states of mind or thought.

It forms all or part of: admonish; Ahura Mazda; ament; amentia; amnesia; amnesty; anamnesis; anamnestic; automatic; automaton; balletomane; comment; compos mentis; dement; demonstrate; Eumenides; idiomatic; maenad; -mancy; mandarin; mania; maniac; manic; mantic; mantis; mantra; memento; mens rea; mental; mention; mentor; mind; Minerva; minnesinger; mnemonic; Mnemosyne; money; monition; monitor; monster; monument; mosaic; Muse; museum; music; muster; premonition; reminiscence; reminiscent; summon.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit manas- "mind, spirit," matih "thought," munih "sage, seer;" Avestan manah- "mind, spirit;" Greek memona "I yearn," mania "madness," mantis "one who divines, prophet, seer;" Latin mens "mind, understanding, reason," memini "I remember," mentio "remembrance;" Lithuanian mintis "thought, idea," Old Church Slavonic mineti "to believe, think," Russian pamjat "memory;" Gothic gamunds, Old English gemynd "memory, remembrance; conscious mind, intellect."

"mental condition characterized by great depression, sluggishness, and aversion to mental action," 1690s, from Modern Latin melancholia (see melancholy).

also psycho-dynamic, 1856, in homeopathic publications, "pertaining to mental powers" (mesmerism, etc.), from psycho- + dynamic (adj.). By 1874 as "pertaining to psychodynamics," the science of the laws of mental action (George Henry Lewes).

"one who scientifically treats or studies mental illness," 1864, from French aliéniste, from alienation in the sense of "insanity, loss of mental faculty," from Latin alienare "deprive of reason, drive mad," literally "to make another's, estrange" (see alienate). The mental sense of alienare has since mostly died out in English, but Middle English had aliened from mind "deranged, not rational" (late 14c.), and alienation was used from 15c. in a sense of "loss or derangement of mental faculties, insanity."

"the science of measuring mental capacities and processes," 1917, from psychometry; also see -ics.