49 certainly synonyms include unquestionably, surely, assuredly, definitely, beyond question, without question, beyond doubt, and undeniably. Certainly is an adverb, and its antonyms are no and possibly. Here are some additional synonyms for "certainly" with example sentences.
49 other ways to say certainly.
He certainly understands the situation now.
I will certainly help you tomorrow.
She will certainly attend the meeting.
They certainly enjoyed their vacation immensely.
You can certainly count on me.