[ def-uh-nit-lee ]
/ ˈdɛf ə nɪt li /
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in a clear and definite manner; unambiguously.
unequivocally; positively.
(used to express complete agreement or strong affirmation): Are you starting your diet tomorrow? Definitely!


Click for a side-by-side comparison of meanings. Use the word comparison feature to learn the differences between similar and commonly confused words.
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Which form is used to state an obligation or duty someone has?

Origin of definitely

First recorded in 1575–85; definite + -ly

synonym study for definitely

1. See clearly.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022


What does definitely mean?

Definitely is an adverb that usually means certainly or without a doubt. It also has this meaning when it’s used as a single-word response.

Definitely is also sometimes used as an adverb to describe an action as clearly defined or precise. When definitely is used as a single word in response to a question or other statement, it is called an interjection or sentence substitute. When used this way, it is very similar to saying certainly or absolutely.

Example: I will definitely be there tomorrow—I promise.

Where does definitely come from?

Definitely is first recorded in English around the early 1580s. It is a combination of the adjective definite (meaning “clearly defined, precise, exact” or “positive, certain, sure”) and the suffix ly, which makes adverbs out of adjectives.

Definitely is frequently used to emphasize the certainty of something or reduce uncertainty, as in Don’t worry—you will definitely be OK. 

Definitely is commonly used as an interjection, or sentence substitute, meaning it does in one word what usually takes a whole sentence to do. When someone asks if you’ll be able to come to their party, instead of saying I’ll definitely be there, you could just say Definitely! When used in this way, definitely often has the added benefit of expressing excitement or enthusiasm. This use is typically considered informal.

Definitely also sometimes gets used as a sentence modifier, meaning it is used at the beginning or end of the sentence to comment on the statement as a whole, as in We’ll get it done, definitely. 

Occasionally, definitely gets used ironically, meaning “not definitely at all,” as in Sure, I would definitely pay a hundred bucks for that piece of junk.

Although their meanings are definitely close, definitely and definitively are used differently, with definitively typically referring to an action that is final or decisive, rather than simply precise or exact.

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What are some other forms of definitely?

What are some synonyms for definitely?

What are some words that share a root or word element with definitely

What are some words that often get used in discussing definitely?

What are some words definitely may be commonly confused with?

How is definitely used in real life?

Definitely is typically used for emphasis, especially when you want to convince someone of the certainty of something. When used as an interjection, it’s usually enthusiastic and informal.



Try using definitely!

Is definitely used correctly in the following sentence?

I definitely want to go tomorrow, but I’m just not sure I can.

How to use definitely in a sentence

British Dictionary definitions for definitely

/ (ˈdɛfɪnɪtlɪ) /

in a definite manner
(sentence modifier) certainlyhe said he was coming, definitely
sentence substitute
unquestionably: used to confirm an assumption by a questioner
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