1) 句首為否定或半否定的詞語，如no, not, never, seldom, little, hardly, at no time, in no way, not until… 等。
Never have I seen such a performance.
Nowhere will you find the answer to this question.
Not until the child fell asleep did the mother leave the room.
當Not until引出主從復合句，主句倒裝，從句不倒裝。
注意： 如否定詞不在句首不倒裝。
I have never seen such a performance.
The mother didn't leave the room until the child fell asleep.
典型例題
1) Why can't I smoke here?
At no time___ in the meeting-room
A. is smoking permitted B. smoking is permitted
C. smoking is it permitted D. does smoking permit
答案A. 這是一個倒裝問題。當否定詞語置于句首以表示強調(diào)時，其句中的主謂須用倒裝結構。 這些否定詞包括no, little, hardly, seldom, never, not only, not until等。本題的正常語序是 Smoking is permitted in the meeting-room at no time.
2) Not until the early years of the 19th century ___ what heat is.
A. man did know B. man know C. didn't man know D. did man know
答案D. 看到Not until…的句型，我們知道為一倒裝句，答案在C，D 中選一個。
