define

American

[dih-fahyn] / dɪˈfaɪn /

verb (used with object)

defined, defining

to state or set forth the meaning of (a word, phrase, etc.).

They disagreed on how to define “liberal.”
to explain or identify the nature or essential qualities of; describe.

to define judicial functions.
to fix or lay down clearly and definitely; specify distinctly.

to define one's responsibilities.

Synonyms:

enumerate, detail, describe, name, state
to determine or fix the boundaries or extent of.

to define property with stakes.
to make clear the outline or form of.

The roof was boldly defined against the sky.

verb (used without object)

defined, defining

to set forth the meaning of a word, phrase, etc.; construct a definition.

define British

/ dɪˈfaɪn /

verb

to state precisely the meaning of (words, terms, etc)
to describe the nature, properties, or essential qualities of
to determine the boundary or extent of
(often passive) to delineate the form or outline of

the shape of the tree was clearly defined by the light behind it
to fix with precision; specify

"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

Other Word Forms

Etymology

Origin of define

First recorded in 1325–75; Middle English def(f)inen, from Anglo-French, Old French definer “to put an end to,” from Latin dēfīnīre ”to limit, define,“ equivalent to dē- “from, away from, out of” + fīnīre “to end”; see origin at de-, finish

Explanation

If you can't define a word, turn to the dictionary. That's always the best way to learn the definition. Likewise, anything you can describe completely is something you can define. The early French and Latin roots of the verb mean something closer to "to limit" or "to create a boundary," but this is really what we do when we define something: we limit its meaning to something specific. So when you're thinking about the word define, remember that you're looking to create a boundary of meaning around it, whether you're specifying the meaning of a word or a larger concept. To define a word such as astronomy is to define both the word and the realm of science that it's concerned with.

Keep Reading on Vocabulary.com

Vocabulary lists containing define

The Language of Standardized Tests, List 1

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Jim Burke's Academic Vocabulary List

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The ACT: The Language of the Test, List 1

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Example Sentences

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

Protists are difficult to define neatly because they are so diverse.

From Science Daily • May 7, 2026

He said: "But wherever you serve, I want to be clear: these events do not define the civil service."

From BBC • May 6, 2026

He is describing what IBM and Cleveland Clinic define as “biologically meaningful molecules.”

From Barron's • May 5, 2026

What happens in the weeks and months to come will define Altman’s legacy.

From The Wall Street Journal • May 3, 2026

I had retreated, fled across an ocean and allowed my father to tell my story for me, to define me to everyone I had ever known.

From "Educated" by Tara Westover

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