English definition of “certainly”
WITHOUT DOUBT › used to emphasize something and show that there is no doubt about it: Their team certainly deserved to win. "Are your parents paying for dinner?" "I certainly hope so." She may never find out. I'm certainly not going to tell her. "Do you regret what you said?" "Certainly not!"
OF COURSE › used to agree to a request: "Could you pass the salt, please?" "Certainly."