supplement

American  

[suhp-luh-muhnt, suhp-luh-ment] / ˈsʌp lə mənt, ˈsʌp ləˌmɛnt /

noun

1. something added to complete a thing, supply a deficiency, or reinforce or extend a whole.

2. a part added to a book, document, etc., to supply additional or later information, correct errors, or the like.

   Synonyms:

   postscript, epilogue, addendum

3. a part, usually of special character, issued as an additional feature of a newspaper or other periodical.

4. Geometry. the quantity by which an angle or an arc falls short of 180° or a semicircle.

---

verb (used with object)

1. to complete, add to, or extend by a supplement.

2. to form a supplement or addition to.

3. to supply (a deficiency).

supplement British  

noun

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. geometry

   1. either of a pair of angles whose sum is 180°

   2. Abbreviation: sup.   supp.  an arc of a circle that when added to another arc forms a semicircle

---

verb

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

Usage

What does supplement mean? A supplement is an addition to something that completes it or makes up for a shortcoming, as in He takes vitamin supplements to make up for his vitamin C deficiency.A supplement is also an addition to a book that provides important information or corrects errors. In this sense, supplement can be confused with the words appendix and index. An appendix gives additional information, such as charts and graphs, but the book or document would be considered complete without it. An index is an alphabetical list of names or topics with page numbers that helps you find something specific in the book, such as all the references to John Wilkes Booth in a biography of Abraham Lincoln.As a verb, supplement means to add to something, as in Tameka sold paintings to supplement her income.In this sense, supplement can be confused with the word complement. Both words mean to add something, but to complement means to add something to make up for a missing piece or element, while to supplement is to add extra information.Example: The company built a new roller coaster to supplement its original roller coaster, which always has a long line.  

Related Words

See appendix. See complement.

Other Word Forms

• supplementation noun
• supplementer noun
• unsupplemented adjective
• well-supplemented adjective

Etymology

Origin of supplement

First recorded in 1350–1400; Middle English, from Latin supplēmentum “that by which anything is made full,” equivalent to sup- sup- + plē- (stem of plēre “to fill”; full ¹ ) + -mentum -ment

Example Sentences

Perplexity and Claude did point out that my iron levels haven’t been tested, and if they’re low, a supplement could increase energy levels.

From The Wall Street Journal • Apr. 4, 2026

In addition, an annual supplement of £440 should be paid on cars with a list price of more than £40,000, or £50,000 for EVs.

From BBC • Mar. 31, 2026

In the kitchen, dozens of supplement bottles line the countertop, each promising a different type of nutritional benefit.

From Slate • Mar. 30, 2026

However, they too can sometimes produce errors, making it necessary to supplement their findings with additional evidence such as open-source data.

From Barron's • Mar. 30, 2026

In connection with the new arrangement, Lawrence received approval for his expanded Alpha II plant, which would supplement the feed from the diffusion process in a final push to produce uranium enriched to weapon-grade.

From "Big Science" by Michael Hiltzik

Related Words

• augment
• build up
• buttress
• complement
• enhance
• enrich
• fill out
• fortify
• improve
• reinforce
• strengthen
• subsidize