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1580s, "offering one or the other of two," from Medieval Latin alternativus, from Latin alternatus, past participle of alternare (see alternate (v.)). Meaning "purporting to be a superior choice to what is in general use" was current by 1970 (earliest reference is to the media); e.g. alternative energy (1975). Related: Alternatively.
1620s, in rhetoric, from Medieval Latin alternativus (see alternative (adj.)). Of courses of action, from 1814. Of objects, etc., "the other of two which may be chosen," by 1838.