From Longman Dictionary of Contemporary Englishcertainly notcertainly notspokenNO used to disagree completely or to refuse to give permission ‘May I go?’ ‘Certainly not!’RegisterIn everyday English, people usually say of course or sure rather than certainly when agreeing or giving permission:‘Can I sit down?’ ‘Of course.’ → certainly
Examples from the Corpus
certainly not• It is certainly not a substitute for good old-fashioned interviewing or communications skills.• Managers may think that a team is doing the work, but it is certainly not a team in any cohesive sense.• Growing deafer, moreover, as they had certainly not been deaf as babies.• And they are certainly not blind to their difficulties or weaknesses.• These recordings are interesting, but certainly not inventive.• But he would be twenty next birthday, a young man certainly, but not mature - certainly not mature.• The pattern is certainly not one of total closure or exclusion.• Nugent is wild on stage but certainly not the stereotypical rock musician. 