alter

UK: /ˈɔːltə^r/ US: /ˈɔltɚ/ ,(ôl′tər)

WordReference Random House Learner's Dictionary of American English © 2026

al•ter /ˈɔltɚ/   v. 

1. to change;
   (to cause to) be different or modified in some way, as size, style, course, or the like: [~ + object]
   to alter a coat.
   [no object]
   Her schedule has altered drastically.
2. Veterinary Diseases to castrate or spay:
   [~ + object] The cat had been altered.

See -alte-.

WordReference Random House Unabridged Dictionary of American English © 2026

al•ter  (ôl′tər), v.t. 

1. 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.
2. Veterinary Diseases to castrate or spay.

v.i. 

3. to change;
   become different or modified.

• Late Latin alterāre to change, worsen, derivative of Latin alter other
• Old French alterer
• Middle English 1350–1400

al′ter•er, n. 
Synonyms

• 1. See adjust, change. 

Al•ter  (ôl′tər), n. 

1. Biographical David, 1807–81, U.S. physicist.

alter., 

1. alteration.

Collins Concise English Dictionary © HarperCollins Publishers::

alter / ˈɔːltə/ verb

1. to make or become different in some respect; change
2. (transitive)
   a euphemistic word for castrate, spay

Etymology: 14th Century: from Old French alterer, from Medieval Latin alterāre to change, from Latin alter other

ˈalterable adjective