verb (used with object)

to make different in some particular, as size, style, course, or the like; modify: to alter a coat; to alter a will; to alter course.
to castrate or spay.

verb (used without object)

to change; become different or modified.

Origin of alter

1350–1400; Middle English < Old French alterer < Late Latin alterāre to change, worsen, derivative of Latin alter other
Related formsal·ter·er, nounhalf-al·tered, adjectivepre·al·ter, verb (used with object)re·al·ter, verbun·al·ter·ing, adjectivewell-al·tered, adjective
Can be confusedaltar alter

Synonym study

1. See adjust, change.




David,1807–81, U.S. physicist.





in alt, in the first octave above the treble staff.

Origin of alt

1525–35; < Provençal < Latin altum, noun use of neuter of altus high


alter idem

[ahl-ter ee-dem; English awl-ter ahy-dem, al-]

noun Latin.

another exactly the same. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for alter

Contemporary Examples of alter

Historical Examples of alter

  • This, I dare say, will make them alter their behaviour to you.

    Clarissa, Volume 1 (of 9)

    Samuel Richardson

  • To this he consents; but he has not courage to alter the family customs.

    Life in London

    Edwin Hodder

  • Christine might be right, but that did not alter things for him.


    Mary Roberts Rinehart

  • They often say in their Gnomic aphorisms, ‘Even the Gods cannot alter the past.’

    De Profundis

    Oscar Wilde

  • It was all in vain, he confesses; he could not alter the convictions of the Empress.

British Dictionary definitions for alter



to make or become different in some respect; change
(tr) informal, mainly US a euphemistic word for castrate, spay
Derived Formsalterable, adjectivealterably, adverbalterability, noun

Word Origin for alter

C14: from Old French alterer, from Medieval Latin alterāre to change, from Latin alter other



(esp of vocal music) high in pitch
of or relating to the octave commencing with the G above the top line of the treble staff


in alt in the octave directly above the treble staff

Word Origin for alt

C16: from Provençal, from Latin altus high, deep
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for alter

late 14c., "to change (something)," from Old French alterer "change, alter," from Medieval Latin alterare "to change," from Latin alter "the other (of the two)," from PIE *al- "beyond" (see alias (adv.)) + comparative suffix -ter (cf. other). Intransitive sense "to become otherwise" first recorded 1580s. Related: Altered; altering.

Online Etymology Dictionary, © 2010 Douglas Harper

alter in Medicine




alanine aminotransferase
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.