al·​ter ˈȯl-tər How to pronounce alter (audio)
altered; altering ˈȯl-t(ə-)riŋ How to pronounce alter (audio)

transitive verb

: to make different without changing into something else
an event that altered the course of history
: castrate, spay
had the puppies altered

intransitive verb

: to become different
customs that alter with the times
alterability noun
alterable adjective
alterably adverb
alterer noun
Choose the Right Synonym for alter

change, alter, vary, modify mean to make or become different.

change implies making either an essential difference often amounting to a loss of original identity or a substitution of one thing for another.

changed the shirt for a larger size

alter implies a difference in some particular respect without suggesting loss of identity.

slightly altered the original design

vary stresses a breaking away from sameness, duplication, or exact repetition.

vary your daily routine

modify suggests a difference that limits, restricts, or adapts to a new purpose.

modified the building for use by the disabled

Examples of alter in a Sentence

Alcohol can alter a person's mood. He altered his will to leave everything to his sister. This one small event altered the course of history. The place has altered in the 10 years since I left. I'll need to have the dress altered before the wedding.
Recent Examples on the Web Combative night the University of Alabama is unlikely to alter the race ahead of voting in Iowa next month Last Updated: Live Coverage Feed 11 hours ago The GOP Debate Is Starting Soon on NewsNation. WSJ, 7 Dec. 2023 Banning marijuana growing at home, increasing the substance’s tax rate and altering how those taxes get distributed are among vast changes Ohio Senate Republicans proposed Monday to a marijuana legalization measure approved by voters last month. Samantha Hendrickson, Fortune, 5 Dec. 2023 The city has started a low-cost spay and neuter program to help remedy the problem, and since June last year has altered about 1,400 animals. Alene Tchekmedyian, Los Angeles Times, 3 Dec. 2023 During the song, Bono altered the lyrics to reflect the death of MacGowan, who passed away Thursday (Nov. 30) following a recent hospitalization. Mitchell Peters, Billboard, 2 Dec. 2023 Bono then altered the lyrics to acknowledge the passing of the Irish songwriting legend and punk singer. Daniel Kreps, Rolling Stone, 2 Dec. 2023 Many of these children might not ever achieve their full potential, because battling chronic illness will alter their lives. Olivia Casey, Scientific American, 1 Dec. 2023 Some scientists warn that drilling could alter trajectories and cause possible collisions. Bret Baier, Fox News, 30 Nov. 2023 The report notes that the global average temperatures through the end of October this year are so much higher than 2016, the current hottest year on record, that the final two months are unlikely to alter the outcome. Siladitya Ray, Forbes, 30 Nov. 2023 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'alter.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


Middle English alteren "to change, transform," borrowed from Anglo-French & Late Latin; Anglo-French alterer, borrowed from Late Latin alterāre, verbal derivative of Latin alter "second, another, next," derivative, with the suffix of opposition -ter-, from the base of alius "other" — more at else entry 1

First Known Use

14th century, in the meaning defined at transitive sense 1

Time Traveler
The first known use of alter was in the 14th century

Dictionary Entries Near alter

Cite this Entry

“Alter.” Dictionary, Merriam-Webster, Accessed 11 Dec. 2023.

Kids Definition


al·​ter ˈȯl-tər How to pronounce alter (audio)
: to change partly but usually not completely
alter a dress
alterability noun
alterable adjective
alterer noun

Middle English alteren "to make different," from Latin alterare (same meaning), from Latin alter "other (of two)" — related to adulterate

Medical Definition


1 of 2 transitive verb
altered; altering


2 of 2 noun
: one of the distinct identities or personality states manifested in an individual with dissociative identity disorder

More from Merriam-Webster on alter

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