adverse (adj.)

late 14c., "contrary, opposing," from Old French advers, earlier avers (13c., Modern French adverse) "antagonistic, unfriendly, contrary, foreign" (as in gent avers "infidel race"), from Latin adversus "turned against, turned toward, fronting, facing," figuratively "hostile, adverse, unfavorable," past participle of advertere "to turn toward," from ad "to" (see ad-) + vertere "to turn, turn back; be turned; convert, transform, translate; be changed" (from PIE root *wer- (2) "to turn, bend"). For distinction of use, see averse. Related: Adversely.