Imagine you’re building a nice little business selling fast food from a mobile van, and the time has come for a face-lift to the notice over the counter. You plan the wording carefully, and opt for the bare minimum: a bare plural noun. What was it that your English teacher used to go on about whenever you used nouns ending in - s? Something about apostrophes? Teacher used to do his nut when you missed them out, so better throw one in just to be safe.

And so the sign goes up over your head: “Sausage’s”.

Why are apostrophes so hard to learn? Perhaps because they’re hard to teach. So here’s our Really Simple Way into possessive apostrophes.

Think of “apostrophe s” - ie the characters ‘s - as an alternative to of, a kind of grammatical badge of ownership. In both cases the badge stands, as expected, between the owner and the thing owned:

the dog of our neighbour

our neighbour ‘s dog

But whereas of puts the dog first, ‘s puts it second.

In most examples both patterns are possible, and sometimes both feel quite comfortable. For example:

the name of the tallest boy

or: the tallest boy ‘s name

But we tend to prefer ‘s with short owners, and of with long ones: the name of the tallest boy in our class

not: the tallest boy in our class ‘s name

We also feel most comfortable with ‘s when the owner is human:

the singer ‘s mouth

but the mouth of the singer.

Examples like these show that apostrophe ‘s really is an alternative to of.

Now let’s look again at the word where panic set in. The trouble with sausages is the plural suffix s, which sounds just like the possessive but should look different (thanks to the apostrophe). What’s the rule for spelling this suffix?

- s if it means plural (or present singular on verbs)

- ‘s if it means “of”

And the dreaded s’ (as in the boys’ fathers)? Easy: always write the apostrophe, but never write an extra s unless you can hear it (as in children’s but not in boys’).

In our experience you can only teach apostrophes effectively if you clearly stress their different purposes - possession (which we’ve covered today) and omission (which we’ll do another time). And the ideal way of building and reinforcing this knowledge until it has been fully internalised is through a series of fast-paced, entertaining starter activities. We owe such activities to our burger-sellers and greengrocers of the future.

Richard Hudson is professor of linguistics at University College London and has advised the National Literacy Strategy team on grammar issues.

Geoff Barton is headteacher of King Edward VI School, Bury St Edmunds, Suffolk