[ awl-ter ]
/ ˈɔl tər /

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 forms

Can be confused

altar alter

Synonym study

1. See adjust, change.

Definition for alter (2 of 5)


[ awl-ter ]
/ ˈɔl tər /


David,1807–81, U.S. physicist.

Definition for alter (3 of 5)


[ alt ]
/ ælt /



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

Definition for alter (4 of 5)

Definition for alter (5 of 5)

alter idem

[ ahl-ter ee-dem; English awl-ter ahy-dem, al- ]
/ ˈɑl tɛr ˈi dɛm; English ˈɔl tər ˈaɪ dɛm, ˈæl- /

noun Latin.

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

Examples from the Web for alter

British Dictionary definitions for alter (1 of 2)


/ (ˈɔːltə) /


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

Derived Forms

alterable, adjectivealterably, adverbalterability, noun

Word Origin for alter

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

British Dictionary definitions for alter (2 of 2)


/ (ælt) music /


(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

Medicine definitions for alter


[ ā′ĕl-tē ]


alanine aminotransferase

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