We put an auxiliary verb before the subject of a clause in several different structures. This is called inversion. Consider the statement She is coming with us, in which the subject she precedes the auxiliary is. In the corresponding YES/NO question Is she coming with us?, the auxiliary is comes before the subject she.
Note that inversion does not occur in indirect questions.
- I don’t know if she is coming with me. (NOT I don’t know if is she coming me?)
Inversion may also occur in certain other circumstances.
In wishes, may often comes before the subject.
- May God bless you.
- May all your dreams come true.
After words like scarcely, hardly, seldom, little, never, rarely etc.
- Little did he realize the danger he faced.
- Never have I seen such a mess.
Sometimes a negative adverb or adverbial expression comes at the beginning of a clause for emphasis. It is usually followed by an auxiliary verb + subject.
- Under no circumstances can we cash cheques.