Without doubt; used to qualify statements
positively, absolutely, unquestionably; see surely.
Without doubt; used to express agreement
assuredly, of course, without fail; see yes.
"certainly." YourDictionary, n.d. Web. 24 May 2018. <http://thesaurus.yourdictionary.com/certainly>.
certainly. (n.d.). Retrieved May 24th, 2018, from http://thesaurus.yourdictionary.com/certainly