Certainly.
The correct spelling is "definitely" (certainly, absolutely).
The adverb is spelled certainly (positively, indeed).
The likely word is definitely (certainly, absolutely).
The idiomatic expression is spelled "of course" (certainly, undoubtedly).
The idomatic phrase is spelled "of course" (certainly, assuredly).
The correct spelling is "definitely" (certainly, absolutely).
The likely word is "absolutely" (positively, certainly).
The adverb is spelled certainly (positively, indeed).
The phrase is spelled "of course" (certainly, surely).
The likely word is definitely (certainly, absolutely).
The idiomatic expression is spelled "of course" (certainly, undoubtedly).
The idomatic phrase is spelled "of course" (certainly, assuredly).
The correct spelling of the adverb is "absolutely" (certainly, positively).
Certainly not the one who can not spell 'coolest' !
The word sought may be the adverb "indeed" (certainly, definitely).
This seems to be a phonetic version of "how do you spell something that you aren't sure of" which would be an "uncertainty." (Which certainly applies here.)
The possible words are:absolutely - certainly, positivelyactually - really, truly, in fact