Etymology
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alter (v.)

late 14c., "to change (something), make different in some way," from Old French alterer "to change, alter," from Medieval Latin alterare "to change," from Latin alter "the other (of the two)," from PIE root *al- (1) "beyond" + comparative suffix -ter (as in other). Intransitive sense "to become otherwise" first recorded 1580s. Related: Altered; altering.

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alter ego (n.)
"second self, counterpart," 1530s, from Latin phrase (used by Cicero), "a second self, a trusted friend" (compare Greek allos ego); see alter and ego.
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unaltered (adj.)
1550s, from un- (1) "not" + past participle of alter (v.).
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alterable (adj.)
1520s, from alter + -able or else from French altérable. Related: Alterably; alterability.
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altercate (v.)

"to contend with words," 1520s, a back-formation from altercation, or else from Latin altercatus, past participle of altercari "to dispute (with another)," from alter "the other" (see alter).

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alternation (n.)

mid-15c., from Old French alternacion "alternation," from Latin alternationem (nominative alternatio) "an interchanging," noun of action from past-participle stem of alternare "to do first one thing then the other; exchange parts," from alternus "one after the other, alternate, in turns, reciprocal," from alter "the other" (see alter).

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alternative (n.)
1620s, in rhetoric, "proposition involving two statements, the acceptance of one implying the rejection of the other," from noun use of Medieval Latin alternativus "do one thing and then another, do by turns," from Latin alternus "one after the other, alternate, in turns, reciprocal," from alter "the other" (see alter). Of courses of action, from 1814. Of objects, etc., "the other of two which may be chosen," by 1836.
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adulteration (n.)

c. 1500, "act of adulterating; state of being debased by mixture with something else," generally of inferior quality, from Latin adulterationem (nominative adulteratio) "an adulteration, sophistication," noun of action from past-participle stem of adulterare "corrupt, falsify; debauch; commit adultery," from ad "to" (see ad-) + alterare "to alter" (see alter), though Watkins explains it as ad alterum "(approaching) another (unlawfully)." Meaning "a result of adulterating" is from 1650s.

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alternative (adj.)
1580s, "offering one or the other of two," from Medieval Latin alternativus, from Latin alternatus, past participle of alternare "do one thing and then another, do by turns," from alternus "one after the other, alternate, in turns, reciprocal," from alter "the other" (see alter). Meaning "purporting to be a superior choice to what is in general use" was current by 1970 (earliest reference is to the media); in popular music, by 1984 in reference to pirate radio. Alternative energy is from 1975. Related: Alternatively.
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altercation (n.)

late 14c., altercacioun, "angry contention with words," from Old French altercacion "altercation" (12c.) and directly from Latin altercationem (nominative altercatio) "a dispute, debate, discussion," noun of action from past-participle stem of altercari "to dispute (with another)," from alter "the other" (see alter). The notion perhaps is of "speaking alternately."

Altercation is the spoken part of a quarrel, the parties speaking alternately. An altercation is thus a quarrelsome dispute between two persons or two sides. [Century Dictionary]
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