This is the 7th most frequent Chinese word.
就
"Just," "then," "right away," or used to indicate emphasis, consequence, or connection.
在条件后连接行为，表示直接跟随的结果。
如果明天下雨，我们就待在家里吧。
If it rains tomorrow, we will just stay at home.
表示因果中的结果。
他很用功，所以考试就考得很好。
Because he studies diligently, he did well in the exam.
表示肯定某个选择，强调决定。