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 Humans have altered the Earth so much that migratory animals are facing extinction Warmth reaches the East Coast by Wednesday. Mary Gilbert, CNN, 23 Feb. 2024 The Knicks believe they were wronged and are seeking a resolution that would give them a chance to alter the game, such as replaying the final 8.3 seconds – the point at which Houston in-bounded the basketball. Jeff Zillgitt, USA TODAY, 23 Feb. 2024 But staffing shortages at Cal-OSHA, plus new limits on district managers’ power to alter citations, have all but guaranteed that appeals are the norm. Maya Miller, Sacramento Bee, 22 Feb. 2024 The idea of therapeutically altering the DNA of a fetus in utero had been floating, opaquely, in the ether since the 1990s, shrouded by issues both technical and ethical in nature. Megan Molteni, STAT, 21 Feb. 2024 Despite the uncertainty of making political predictions, money managers are already contemplating how the election could alter the mood in markets. Joe Rennison, New York Times, 20 Feb. 2024 The bureau concluded that Ms. Gilchrist often falsified DNA tests, committed perjury, and altered or destroyed evidence. Riley Robinson, The Christian Science Monitor, 18 Feb. 2024 Returning officers, who are bound by law to compile and deliver the numbers from their constituencies to the Election Commission of Pakistan (ECP) by 2 a.m. on the day following the election, failed to do so – sparking fears that the results were being altered. Hasan Ali, The Christian Science Monitor, 9 Feb. 2024 Crowds gathered at a church in Halberstadt, Germany, this week to observe the instrument as volunteers added a pipe to slightly alter its song. Sonja Anderson, Smithsonian Magazine, 9 Feb. 2024 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 26 Feb. 2024.

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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