In English Grammar‏‎ we talk about inversion when we change the normal order of the elements in a sentence.

In most cases this means swapping the position of the subject and verb of the sentence. For example, this is a common sentence structure in English which follows the pattern:

{subject} + {verb} + {…}

Peter is French.

You are happy.

But if we turn it into a question, we invert the normal pattern and have

{verb} + {subject} + {…}

Is Peter French?

Are you happy?

Usage

You can see that inversion is used a lot when we make questions‏‎ as above.

However, it can also used with adverbs‏‎ of place as in this example.

A young man + stood + against the wall.

Against the wall + a young man + stood.

Against the wall + stood + a young man.

We can replace if in a conditional with an inversion when we use were, had or should:

If you were younger, you could get in free.
Were + you younger, you could get in free.

If I had seen you, I would have asked you to the party.
Had + I seen you, I would have asked you to the party.

If you should want anything, please call me.
Should + you want anything, please call me.

When we make comparisons with the conjunctions‏‎ as, we can also use inversion.

She is beautiful, as her daughter is.
She is beautiful, as is her daughter.

When we use an adverbial phrase starting with only at the beginning of a sentence, we use inversion:

Only when I saw him, did I realise how much he had grown.
Only in England does it rain on bank holidays.

N.B. With not only, we often use but also:

Not only had we lost our coats but also our wallets.

Many negative adverbials take inversion:

Under no circumstances will she…

Seldom have I…

Rarely do we…

Never have I…

Never before has it…

On no account must you…

Not until I…did I…

Hardly had I…when…

Scarcely had we…than…

No sooner had she…than…

So {adjective} was he…that…

We also use inversion with neither, nor & so.

Inversion and the TEFL Class

Should you teach inversion in your TEFL class?

We would suggest that you do not devote a full lesson or more to teaching inversion but to mention it if the subject comes up in class. You should be aware of inversion and when it occurs, but only when it causes a problem should you discuss it with your students and then give them an exercise or two to identify when inversion should be used and how to form a good inversion.