apnea n.

prefix meaning "not, without," from Greek a-, an- "not" (the "alpha privative"), from PIE root *ne- "not" (source also of English un-).

In words from Greek, such as abysmal, adamant, amethyst; also partly nativized as a prefix of negation (asexual, amoral, agnostic). The ancient alpha privatum, denoting want or absence.

Greek also had an alpha copulativum, a- or ha-, expressing union or likeness, which is the a- expressing "together" in acolyte, acoustic, Adelphi, etc. It is from PIE root *sem- (1) "one; as one, together with."

a word used in English in various sense from late 19c. ("breath;" "spirit;" "soul;" "a breathing;" also as a technical term), from Greek pneuma "a blowing, a wind, blast; breeze; influence; breathed air, breath; odor, scent; spirit of a person; inspiration, a spirit, ghost," from pnein "to blow, to breathe," from PIE root *pneu- "to breathe," of imitative origin (compare Greek pnoe "breath," pnoia "breathing;" Old English fnora "sneezing," fnæran "to snort").