副詞N4

必ず

surely / without fail / always

Structure

必ず + V / 文

An adverb meaning "surely, without fail". 必ず emphasizes certainty or obligation; unlike きっと it carries no speculation. E.g., 必ず来てください.

約束の時間には必ず来てください。

Please come without fail at the appointed time.

早起きすれば、必ず間に合いますよ。

If you get up early, you'll surely make it in time.

必ず is more certain than きっと and has no speculative nuance. 必ずしも〜ない means "not necessarily...".