supplement

UK: /ˈsʌplɪmənt/, /ˈsʌplɪmɛnt/

US: /n. ˈsʌpləmənt; v. -ˌmɛnt/

US: (n. sup′lə mənt; v. sup′lə ment′)

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

sup•ple•ment /n. ˈsʌpləmənt; v. -ˌmɛnt/   n. [countable]

1. something added to complete a thing or to reinforce or extend something:
   The supplies at the depot were a supplement to what they had already brought with them.
2. Printing, Library Science something added to or issued after a publication that supplies further information, etc.:
   a supplement to an encyclopedia.
3. Mathematics the amount by which an angle or arc falls short of 180° or a semicircle.

v. [~ + object]

4. to complete, add to, or extend by a supplement:
   The computer can supplement what has been taught in a classroom.

sup•ple•men•tal, adj. 

WordReference Random House Unabridged Dictionary of American English © 2026

sup•ple•ment  (n. sup′lə mənt;v. sup′lə ment′), n. 

1. something added to complete a thing, supply a deficiency, or reinforce or extend a whole.
2. Printing a part added to a book, document, etc., to supply additional or later information, correct errors, or the like.
3. a part, usually of special character, issued as an additional feature of a newspaper or other periodical.
4. Mathematics [Geom.] the quantity by which an angle or an arc falls short of 180° or a semicircle.

v.t. 

5. to complete, add to, or extend by a supplement.
6. to form a supplement or addition to.
7. to supply (a deficiency).

• Latin supplēmentum that by which anything is made full, equivalent. to sup- sup- + plē- (stem of plēre to fill; see full¹) + -mentum -ment
• Middle English 1350–1400

sup′ple•ment′er, n. 
Synonyms

• 2. addendum, epilogue, postscript. See appendix. 
• 5. See complement. 

Collins Concise English Dictionary © HarperCollins Publishers::

supplement noun / ˈsʌplɪmənt/

1. an addition designed to complete, make up for a deficiency, etc
2. a section appended to a publication to supply further information, correct errors, etc
3. a magazine or section inserted into a newspaper or periodical, such as one with colour photographs issued every week
4. either of a pair of angles whose sum is 180°
5. an arc of a circle that when added to another arc forms a semicircle

verb / ˈsʌplɪˌmɛnt/

1. (transitive) to provide a supplement to, esp in order to remedy a deficiency

Etymology: 14th Century: from Latin supplēmentum, from supplēre to supply¹

ˌsupplemenˈtation noun