definitely vs decidedly

definitely and decidedly both are adverbs.

Word	Noun	Adjective	Verb	Adverb
definitely	No	No	No	Yes
decidedly	No	No	No	Yes

As adverbs, definitely and decidedly are synonyms defined as:

Other synonyms of definitely include by all odds, emphatically, in spades, unquestionably.

definitely (adverb)	decidedly (adverb)
without question and beyond doubt	without question and beyond doubt