• We invert the subject and auxiliary in the sentence to give emphasis.

E.g.

1) Seldom have there been such busy days in the old bookshop.

2) Rarely do we have any rain at this time of year.

  • We use inversion after adverbs with negative or restrictive meaning, such as

never, nowhere, rarely, hardly, little, seldom:

Little did she realise that her long-cherished dream would come true one day.

Never will there be another chance!

Hardly ever did he wear formal clothes.

  • after adverbial phrases with negative or restrictive meaning, such as

only once, only later, only then, only by chance, only in this way, in no way, on no account, under no circumstances, at no time, not until:

Only by chance has this marginal party won so many seats.

On no account should you reveal your identity.

Under no circumstances can we agree to these terms.

  • after clauses with negative or restrictive meaning, such as only when/after/if; not until; not since:

Only when Jeremy Corbyn apologized to David Cameron for his rude words did the Speaker resume the session.

Not until the plane took off did he realise that he had left his wallet behind.

Note: Inversion occurs after the clause, not within it!

Only when have I finished my term project I will be able to make any holiday preparations.

Only when I have finished my term project will I be able to make any holiday preparations.

  • in patterns that indicate a prevented action

No sooner… than

Hardly… when

Note: in most cases past perfect tense is used in these patterns

Hardly had Dr. Martin prepared to have his lunch when he was called back to the surgery.

No sooner had I made myself comfortable in the chair than the phone rang.

  • after phrases so + adjective; such + noun

So tiring was the ascent that the climbers had to rest every now and then.

Such a smart student was he that he graduated with honors.

  • after Neither…/ Nor… to start a sentence with a negative addition to a previous negative clause or sentence:

The professors were not happy to know about the plans to extend the academic year. Nor were the students.

I cannot give you my blessing, nor can I wish you good fortune.

  • after Not only…but also

Not only is this car fuel-efficient, but it is also beautifully designed.

  • in some types of conditional clauses.

INVERSION IN CONDITIONAL SENTENCES

Instead of “if” we use should, were to, had in types 1, 2, 3 respectively.

Type 1:

If you need more information, feel free to contact our head office.

Type 2:

A full-fledged war would break out if the peace talks failed.

Type 3:

If they had booked in advance, they wouldn’t have to pay…..

INVERSION:

Should you need more information, feel free to contact our head office.

INVERSION:

A full-fledged war would break out, were the peace talks to fail.

INVERSION:

Had they booked in advance, they wouldn’t have to pay….