Use the apostrophe with contractions. The apostrophe always replaces the missing letter.

Do not – Don’t

Is Not – Isn’t

He has arrived – He’s arrived

Use the apostrophe to show possession—that something belongs to someone.

The woman’s coat

The man’s umbrella

The cat’s whiskers

The bishop’s finger

Tames’s house

Note: Although names ending in "s" or an "s" sound do not require the second "s" when used in the possessive form, most people prefer to use it

Use the apostrophe when the noun is implied.

‘This is your carrot. This is my horse’s’

When using plural possession, make the plural first and then place the apostrophe after it.

The apples’ flavour was bitter.

The three windows’ light

The flavour of the apples was bitter. (no apostrophes, because no possession)

The light from three windows (no apostrophes, because no possession)

Don’t use the apostrophe for the plural of a name.

They mentioned the Browns on the news.

The Johnsons attended the wedding.

If two or more people possess the same thing, only use apostrophe ‘s’ after the second person.

Jack and Jill’s bucket

Phil and Graham’s wedding

Nobody would think of using an apostrophe with the word "mine", but lots of people get confused by the "s" in other possessive pronouns like his, hers, its, theirs, ours, yours and whose. No apostrophe is required here even though it is possessive.

This bowl is yours.

That tree has a ball wedged in its branches.

Whose wallet is this? It is not theirs.

Only ever use "it’s" for a contraction of "it is" or "it has".

It’s cloudy today.

It’s been cloudy today.

The plurals for capitals or numbers used as nouns do not use apostrophes.

I have just sat my SATs. (Not SAT’s)

That was normal during the 1980s. (Not 1980’s)

Nobody buys DVDs anymore. (Not DVD’s)

The apostrophe goes after the thing doing the possessing.

The moon’s reflection (the reflection of the moon)

A week’s pay (the pay of a week)

Two week’s pay (the pay of two weeks)

Everyone’s choice (the choice of everyone)

Finally, in most cases, phrases such as "girls school", "Fathers Day", "visitors book" and "workers canteen" should not include apostrophes because there is no possession involved.

Girls school: a school for girls, not owned by girls

Visitors book: a book for visitors, not owned by visitors

However, there are a few exceptions such as All Saints’ Day and All Souls’ Day, which do have apostrophe even though they are not owned by saints/souls.

This is an excerpt from Grammar Geek by Michael Powell, published by Cassell, £8.99

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