definitely

adverb

1. in a clear and definite manner; unambiguously.
2. unequivocally; positively.

interjection

3. (used to express complete agreement or strong affirmation): Are you starting your diet tomorrow? Definitely!

adverb

1. in a definite manner
2. (sentence modifier) certainlyhe said he was coming, definitely

sentence substitute

3. unquestionably: used to confirm an assumption by a questioner

adv.

1580s, from definite + -ly (2). As a colloquial emphatic word, attested by 1931.