题目内容：

Not until he left his home did he begin to know how important the family was for him
为什么不是not did he begin to know how important the family was for him until he left his home.

优质解答

not until 的倒装句型,将not until 提前 所以主句部分 倒装.

追问：

是规定，必须要not until都在句首？

追答：

不是规定 ，看哪一部分倒装 就用什么样的句型