American

[kom-pluh-muhnt, kom-pluh-ment] / ˈkɒm plə mənt, ˈkɒm pləˌmɛnt /

noun

complements
plural

something that completes or makes perfect.

A good wine is a complement to a good meal.
the quantity or amount that completes anything.

We now have a full complement of packers.
either of two parts or things needed to complete the whole; counterpart.
full quantity or amount; complete allowance.
the full number of officers and crew required on a ship.
Grammar.
1. a word or group of words that completes a grammatical construction in the predicate and that describes or is identified with the subject or object, as small in The house is small or president in They elected her president.
2. any word or group of words used to complete a grammatical construction, especially in the predicate, including adverbials, as on the table in He put it on the table, infinitives, as to go in They are ready to go, and sometimes objects, as ball in He caught the ball.
Geometry. the quantity by which an angle or an arc falls short of 90° or a quarter of a circle.
Also called absolute complement. Mathematics. the set of all the elements of a universal set not included in a given set.
Music. the interval that completes an octave when added to a given interval.
Immunology.
1. a system in vertebrate blood of 12 or more proteins that react in a cascade to a cell displaying immune complexes or foreign surfaces, acting in various combinations to coat the cell and promote phagocytosis, make holes in the cell wall, or enhance the inflammatory response.
2. any of the proteins in the complement system, designated C1, C2, etc.
complementary color.

verb (used with object)

complements,
present (3rd person singular)
complemented,
past participle, past
complementing
present participle

to complete; form a complement to.

This belt complements the dress better than that one.
Obsolete. to compliment.

verb (used without object)

complements,
present (3rd person singular)
complemented,
past participle, past
complementing
present participle

Obsolete. to compliment.

complement British

noun

a person or thing that completes something
one of two parts that make up a whole or complete each other
a complete amount, number, etc (often in the phrase full complement )
the officers and crew needed to man a ship
grammar
1. a noun phrase that follows a copula or similar verb, as for example an idiot in the sentence He is an idiot
2. a clause that serves as the subject or direct object of a verb or the direct object of a preposition, as for example that he would be early in the sentence I hoped that he would be early
maths the angle that when added to a specified angle produces a right angle
logic maths the class of all things, or of all members of a given universe of discourse, that are not members of a given set
music the inverted form of an interval that, when added to the interval, completes the octave

the sixth is the complement of the third
immunol a group of proteins in the blood serum that, when activated by antibodies, causes destruction of alien cells, such as bacteria

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

verb

(tr) to add to, make complete, or form a complement to

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

complement Scientific

/ kŏm′plə-mənt /

A group of proteins in blood serum that interact systematically as part of the body's immune response to destroy disease-causing antigens, especially bacteria. Complement proteins interact with antibodies and other chemical substances to cause the disintegration of foreign cells and enhance other immune functions such as phagocytosis.
A complementary color.

Usage

What’s the difference between complement and compliment? The word complement most commonly refers to something that goes along with something else and serves to make it better or complete it. It’s also commonly used as a verb meaning to serve as a complement in this way, as in That necklace really complements the rest of your outfit. A compliment is a comment intended to express praise or admiration of someone. Compliment is also commonly used as a verb meaning to give a compliment. Complement has many other specific meanings, but compliment is really only used to refer to a nice comment or the action of giving one. Since the primary senses of both words are generally used in positive contexts, it can be easy to confuse them. The adjective form of complement is complementary, as in complementary colors. The adjective form of compliment is complimentary, which can describe something intended to be a compliment, as in complimentary remark, or it can be used to mean that something is given for free, as in I hope we get complimentary snacks on this flight. The easiest way to remember the difference is that complement often means to complete, and complete also starts with c-o-m-p-l-e. On the other hand, compliment is spelled with an i, and compliments are something that I like to get (and give). Nice shirt, by the way. Here’s an example of complement and compliment used correctly in the same sentence. Example: The chef overheard the diners at one table complimenting the way the sauce complemented the fish, so she told the server to offer them a complimentary dessert. Want to learn more? Read the full breakdown of the difference between complement and compliment.

Commonly Confused

Complement and compliment, which are pronounced alike and originally shared some meanings, have become separate words with entirely different meanings. As a noun, complement means “something that completes or makes perfect”: The rare old brandy was a perfect complement to the delicious meal. As a verb, complement means “to complete”: A bright scarf complements a dark suit. The noun compliment means “an expression of praise, commendation, or admiration”: The members paid her the compliment of a standing ovation. The verb compliment means “to pay a compliment to”: Everyone complimented him after the recital.

See compliment

Synonym Usage

Complement, supplement both mean to make additions to something. To complement is to provide something felt to be lacking or needed; it is often applied to putting together two things, each of which supplies what is lacking in the other, to make a complete whole: Two statements from different points of view may complement each other. To supplement is merely to add to: Some additional remarks may supplement his address.

Other Word Forms

Derived Forms

complementer

noun

Inflected Forms

complements

plural

Conjugated Forms

Etymology

Origin of complement

First recorded in 1350–1400; Middle English, from Latin complēmentum “something that completes,” equivalent to complē(re) “to fill, fill up” + -mentum noun suffix; see origin at complete, -ment

Explanation

A complement is something that makes up a satisfying whole with something else. Those shiny red shoes you just bought complement your shiny red purse. Complement comes from the Latin complementum, "something that fills up or completes." Complement keeps both the e and the meaning. It's also a verb; if you and your partner complement each other, you make a perfect pair. Something that complements completes or adds a little something.

Keep Reading on Vocabulary.com

Vocabulary lists containing complement

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

See Examples For:

complement complements complemented complementing

Draped in a torn white skirt and black fishnet gloves to complement, she wailed “I hate when girls die.”

From Los Angeles Times ● Aug. 30, 2026

Goldman’s economists argue that currency revaluation would complement domestic reforms by sustaining growth as the trade surplus shrinks.

From The Wall Street Journal ● Aug. 28, 2026

C3 drew particular attention because earlier research has suggested that activation of the complement system, a network of proteins that helps defend the body against pathogens, may contribute to chronic inflammation.

From Science Daily ● Aug. 26, 2026

"Just to narrow it down to the subtypes of macrophages responsible for this complement protein production was very challenging."

From Science Daily ● Aug. 26, 2026

Recall from chapter 4 that grammatical categories like adjective are not the same thing as grammatical functions like modifier and complement.

From "The Sense of Style" by Steven Pinker

Its more mobile footprint in the Philippines complements the U.S. presence in Japan, where America has permanent bases that host tens of thousands of troops.

From The Wall Street Journal ● Aug. 19, 2026

Each one has her singular presence — Trachtenberg plucky and inspiring; Panettiere charming and bold — but together, they’re beautiful complements.

From Salon ● Aug. 18, 2026

Ed Bartlam, co-founder of Underbelly, said: "Set against the magnificent backdrop of St George's Hall, we're looking forward to working with the local community to create a new seasonal highlight that complements Liverpool's festive calendar."

From BBC ● Aug. 7, 2026

The group is pushing for the creation of more guardrails, incentives and institutions to “steer AI in a direction that complements humans and benefits society.”

From Los Angeles Times ● Jul. 14, 2026

Her day dress is buttercup yellow and perfectly complements her new skin color—a dusky light brown, like warmed milk with cinnamon and nutmeg stirred into it.

From "The Belles" by Dhonielle Clayton

The stories of dead Jews, Ms. Horn reminds us, must be complemented by an understanding of the traditions, texts and practices of living ones.

From The Wall Street Journal ● Aug. 31, 2026

Another considered a deep-green leotard whose verdant shade complemented the florals of her wrap skirt.

From Los Angeles Times ● Aug. 11, 2026

The 20-year-old's huge serve and defensive solidity is complemented by fluid movement, best demonstrated in a magnificent quarter-final win over Brazilian teenager Joao Fonseca.

From BBC ● Jun. 5, 2026

By the 2000s, some franchises offered games that fleshed out or complemented the worlds depicted on the silver screen.

From Barron's ● May 26, 2026

Fond of costumes, Sandy appeared wearing a high-altitude climbing suit over her evening dress, complemented by mountaineering boots, crampons, ice ax, and a bandolier of carabiners.

From "Into Thin Air" by Jon Krakauer

Washington noted that higher usage of agentic work units is complementing core seat growth.

From MarketWatch ● Aug. 26, 2026

“We are excited to see ramping growth in the Wayfair business and complementing that with outsized growth from our specialty and luxury brands,” he said.

From The Wall Street Journal ● Aug. 4, 2026

If L7 was a statement, Finch was its punctuation, her crayon-bright hair complementing a radiant humanity.

From Salon ● Jul. 21, 2026

Ducks owner Henry Samueli has denied interest in the Angels, but he could consider extending and complementing his OC Vibe development across the 57 Freeway — and his hockey team already wears the Anaheim name.

From Los Angeles Times ● Apr. 17, 2026

They wear fashionable gowns that do not match exactly but coordinate beautifully, one complementing the other.

From "The Night Circus" by Erin Morgenstern

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023