"able or tending to depress," 1610s, from Latin depress-, past-participle stem of deprimere (see depress) + -ive. In psychology, from 1905. Related: Depressiveness.

"pertaining to or affected with mania," 1902, from mania + -ic. The clinical term manic depressive also is from 1902; manic depression is first attested 1903. An older name for it was circular insanity (1857), from French folie circulaire (1854).

1847, "mental affection or derangement," Modern Latin, from Greek psykhē "mind, life, soul" (see psyche) + -osis "abnormal condition." Greek psykhosis meant "a giving of life; animation; principle of life."

"having two poles;" see bi- "two" + polar. It is attested from 1810 in the figurative sense of "of double aspect;" by 1859 with reference to anatomy ("having two processes from opposite poles," of nerve cells). Psychiatric use in reference to what had been called manic-depressive psychosis is said to have begun 1957 with German psychiatrist Karl Leonhard. The term became popular early 1990s. Bipolar disorder was in DSM III (1980).

"of or pertaining to psychosis," 1889, coined from psychosis, on the model of neurotic/neurosis; ultimately from Greek psykhē "understanding, the mind (as the seat of thought), faculty of reason" (see psyche). Related: Psychotically.

"manic elation accompanied by quickened perception," 1843 (as a clinical word from 1882, from German hypomanie, 1881); see hypo- "under, beneath" + mania. Related: Hypomaniac; hypomanic.

1776, "functional derangement arising from disorders of the nervous system (not caused by a lesion or injury)," coined by Scottish physician William Cullen (1710-1790) from Greek neuron "nerve" (see neuro-) + Modern Latin -osis "abnormal condition." Originally of epilepsy, hysteria, neuralgia, etc. Used in a general psychological sense from 1871, "change in the nerve cells of the brain resulting in symptoms of stress," but not radical loss of touch with reality (psychosis); clinical use in psychiatry dates from 1923.

1570s, "diseased, sickly" (a sense now obsolete); 1580s, "broken, impaired, full of cracks or flaws," from craze + -y (2). Meaning "deranged, demented, of unsound mind or behaving as so" is from 1610s. Jazz slang sense "cool, exciting" is attested by 1927. Related: Crazily; craziness.

To drive (someone) crazy is attested by 1873. To do something like crazy "with manic vigor or frequency" is by 1905. Phrase crazy like a fox has origins by 1935. Crazy Horse, name of the Teton Lakhota (Siouan) war leader (d. 1877), translates thašuka witko, literally "his horse is crazy." Crazy-quilt (1886) preserves the original "break to pieces" sense of craze (v.). Crazy bone as an alternative to funny bone is recorded by 1853.

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."