Certainly

Part of speech: adverb

Pronunciation: /ˈsɜː.tn̩.li/

Definitions

1. Without doubt or hesitation; in a way that is sure or definite
2. In a manner that leaves no room for uncertainty or disbelief
3. Expressing complete confidence that something is true or will happen

Etymology: "Certainly" is a plain formation: the adjective "certain" with the suffix "-ly" attached, turning it into an adverb meaning in a sure or definite manner. The adjective itself came into English from Old French "certain," descended from Latin "certus," meaning "decided" or "fixed," the same root behind "certify" and "certitude." The adverb took shape in Middle English as "certeynly," and its sense has stayed close to the adjective's from the start: something done certainly is done with no doubt about it. Its everyday use as a polite reply, meaning "yes, of course," grows naturally from that sense of being sure.

Synonyms: definitely, undoubtedly, surely, absolutely, positively

Antonyms: doubtfully, uncertainly, hesitantly