Beginning a sentence with a negative word
An inversion is a powerful tool that you can use to stress the uniqueness of an action. Note that inversion is mainly used when the sentence begins with a negative word.
When a sentence begins with a negative adverbial like never, rarely or seldom, the auxiliary verb comes before the subject. Note that these time expressions are normally used with a perfect verb form or modal auxiliary verbs. Comparative forms are also common.
Never have I seen anything stranger.
Seldom have I heard anything more ridiculous.
Time expressions: hardly, barely, no sooner, or scarcely
Sentences beginning with these time expressions also have an inverted word order. These expressions are used to talk about a succession of events in the past.
Scarcely had I reached the station when the train arrived.
Scarcely had I closed my eyes when the doorbell rang.
No sooner had I closed the door than somebody knocked.
Hardly had I arrived when trouble started.
After expressions with only
Inversion is possible after expressions like only after, only when and only then.
Only then did I understand what the problem was.
Only after her death was I able to understand her.
‘Little’ is used in a negative sense.
Little did I understand the gravity of the situation.
Little did she realize the danger she faced.
Inversion after ‘So’, ‘Such’, and ‘That’
Inversion is also possible after so, such and that.
‘I am hungry.’ ‘So am I.’
So strange was the situation that I couldn’t understand anything.
In formal and literary conditional clauses, an auxiliary verb can be put before the subject instead of using if.
Were she my daughter I wouldn’t let her wear these kinds of clothes. (= If she were my daughter, I wouldn’t let her wear these kinds of clothes.)