1550s, "occurring or acting by turns, one after the other," present-participle adjective from alternate (v.). Electrical alternating current is recorded from 1839, an electrical current which flows alternately in opposite directions without interruption.
alternating feelings of love and hate
alternating current
alteration
altercate
altercation
alternate
alternately
alternating
alternation
alternative
alternator
although
alti-
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