Chiasmus.

Sounds almost gynaecological doesn't it.

In Greek this letter is pronounced like the ch in loch – Chi. As in Christmas, chiropody and chiropractor. It looks – and you need to pay attention here – like this:

And you can use it in sentences too – a crossover which is rather clever.

Like this:

Nature is not symmetrical; and symmetry is not natural.

Explanation:

Nature is not symmetrical; and symmetry is not natural.

Bruce Forsyth made a career out of his 

“Nice to see you!” Audience shouts back: “To see you nice!”

The three musketeers:

One for all, and all for one!

As Plato never said: Eat to live or live to eat.

We must bring our enemies to justice – or justice to our enemies.

How to construct your own chiasmus:

Think of two words which go with your idea: handsome celebrity

A celebrity has to be handsome, but you don't have to be handsome to be a celebrity. Then start talking about your chosen celebrity.

Terrible and frightening.

Frightening is something terrible, but something terrible is not something to be frightened of. Then start talking about your recent operation.

It can be very simple:

I like dogs; dogs like me. Now tell about the dog who unexpectedly went for you on your walk through Exmoor.

A Level Students only:

What use is the Chiasmus in exams though?

Well, a half decent examiner will spot a chiasmus a mile off and s/he will then be right behind you looking for ways to increase your mark. Increasing your mark is just what you want from an examiner who is right behind you.

Henry VIII married six wives, but let us not forget that six wives married Henry VIII. 

We can then start talking about his wives from their point of view.

Or Henry VIII liked insulting Francis of France, but Francis liked insulting Henry too. 

You can then trot out the foreign policy which you so carefully revised.

Chiasmus gives the impression of giving both points of view; both points of view are the essence of chiasmus.

(Added emphasis is most important for exams because exams depend on added emphasis.)