きっと

きっと means "surely", "I'm sure": you are confident about something you can't know for a fact – how things will turn out, or what someone else is doing or feeling. It goes before the part of the sentence it covers, and the sentence often ends in だろう, でしょう or とおもう思う.

The guess can be about now or about the past as well as the future.

きっと, たぶん and 必ず

たぶん is weaker: "probably". かならず必ず is not a guess at all. It says something happens every time, or that you will make sure it does, so a habit or a rule takes 必ず.

• × 毎朝きっと六時に起きます → 毎朝必ず六時に起きます