What does definitely mean?
"Definitely" is an adverb used to express complete certainty, emphasizing that something is true, will happen, or should be regarded as beyond doubt. It answers questions of likelihood with firmness: if someone says they will "definitely" attend an event, no uncertainty remains. The word functions as an intensifier in everyday speech and writing, often appearing before the verb or clause it strengthens ("I definitely agree") or standing alone as an emphatic reply ("Definitely!"). Its tone is emphatic but broadly neutral, fitting casual conversation as comfortably as professional correspondence, though highly formal texts sometimes favor alternatives such as "certainly" or "undoubtedly." Derived from the Latin root definire, meaning to set limits or determine precisely, the word carries a sense of fixedness and resolution. Because it communicates conviction so directly, "definitely" is among the most useful adverbs for making statements sound confident and decisive rather than hedged or tentative.
adverbWithout doubt or uncertainty; certainly and unequivocally.
- Used to emphasize that something is certain and without doubt; unquestionably.
- Used to give a firm affirmative answer or agreement; yes, absolutely.
"She will definitely be at the meeting tomorrow morning."
"The train has definitely left already — we should call a taxi instead."
""Are you coming to the party?" "Definitely!""
"That was definitely the best meal I've had all year."
One of the most commonly misspelled words in English, "definitely" is so frequently written as "definately" that autocorrect systems treat the error as almost inevitable.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of definitely
"Definitely" derives from the adjective "definite," which entered English in the 16th century from Latin definitus, the past participle of definire, meaning "to set bounds to" or "to determine precisely." That Latin verb combines de- (indicating completion) with finire, "to limit or finish," itself rooted in finis, meaning "boundary" or "end." The adverb formed in English during the 16th century by adding the suffix -ly. It shares this Latin ancestry with related words such as "define," "definition," and "definitive," all of which preserve the core idea of drawing clear boundaries around a concept — hence its modern sense of leaving no room for doubt.
How definitely is actually used
"Definitely" is common in both formal and informal registers but appears especially often in spoken English, where it serves as a strong, emphatic way to agree or confirm. In very formal writing, "certainly" or "undoubtedly" may be preferred. It typically modifies verbs, adjectives, or whole clauses and usually sits before the word it emphasizes, though it can also open a sentence for stronger emphasis. Avoid using more than one intensifier alongside it (e.g., *"very definitely definitely"*) as this can sound awkward or redundant.
Easily confused with definitely
"Definitely" means with certainty, while "defiantly" means in a bold, rebellious manner — the two are often confused because of their similar spelling.
"Definitely" expresses certainty about something, whereas "definitively" means conclusively or finally settling a matter.