alter

verb

al·​ter ˈȯl-tər 

altered; altering ˈȯl-t(ə-)riŋ 

transitive verb

1

: to make different without changing into something else

an event that altered the course of history

2

: castrate, spay

had the puppies altered

intransitive verb

: to become different

customs that alter with the times

alterability

ˌȯl-t(ə-)rə-ˈbi-lə-tē 

noun

alterable

ˈȯl-t(ə-)rə-bəl 

adjective

alterably

ˈȯl-t(ə-)rə-blē 

adverb

alterer

ˈȯl-tər-ər 

noun

Synonyms of alter

• modify
• change
• remodel

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

The innovation focuses on a self-sustaining electronic system that combines wireless information transfer with energy harvesting, potentially altering the current methods used in electronic warfare and wireless networking. —Aman Tripathi, Interesting Engineering, 28 Dec. 2025

With the short-term funding bill only lasting through the end of January, consumers could alter their spending once again – a factor that could ultimately have an impact on investor sentiment. —Sean Conlon, CNBC, 28 Dec. 2025

Why Cold Pizza May Have Resistant Starch Everything from storage duration to serving temperature can alter the resistant starch levels in food, Meghan Windham, MPH, RD, LD, clinical assistant professor at Texas A&M University, told Verywell. —Eleesha Lockett, Verywell Health, 27 Dec. 2025

And the erratic way the president rolled out his tariffs — announcing them, then suspending or altering them before conjuring up new ones — made 2025 one of the most turbulent economic years in recent memory. —Wyatte Grantham-Philips, Fortune, 26 Dec. 2025

Word History

Etymology

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

Phrases Containing alter

• alter ego

Rhymes for alter

• altar
• falter
• halter
• psalter
• salter
• defaulter

Kids Definition

alter

verb

al·​ter ˈȯl-tər 

1

: to change partly but usually not completely

alter a dress

2

: castrate, spay

alterability

ˌȯl-t(ə-)rə-ˈbil-ə-tē 

noun

alterable

ˈȯl-t(ə-)rə-bəl 

adjective

alterer noun

Etymology

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

Medical Definition

alter

1 of 2 transitive verb

al·​ter

ˈȯl-tər

altered; altering

-t(ə-)riŋ

: castrate sense 1, spay

alter

2 of 2 noun

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