Writers often use apostrophes to show that somebody (or something) owns something. In these cases they are called possessive apostrophes, even though the ownership is not always real.

Some examples of possessive apostrophes are:

the students’ pens, the editor’s chair
the child’s mother, the computers’ dust covers.

Writers also use apostrophes when they miss out a letter in quoting informal speech or writing in an informal style.

For example:

it’s a winner I’ve won
that’s true they’re back,

Apostrophes are almost never used to make plurals of figures or letters.

For example:

There are 100s of QCs who want to become MPs.

No apostrophes are necessary here. In any case, in sentences where figures are plural, it’s better to spell them out, as in seven fours are 28.

Probably the only legitimate reason for using an apostrophe to form a plural is in dealing with lower-case letters, as in mind your p’s and q’s or in referring to do’s and don’ts. These are not phrases that occur very often in news writing and the general rule is that an apostrophe must show either possession or omission.

Basic possessive apostrophes.

In the first set of examples above, there is real ownership only in the case of the students’ pens. The editor doesn’t really own his office chair, the child doesn’t own its mother and computers can’t own anything.

However, for grammatical purposes, all four apostrophes are possessive.

Some people have problems in deciding which word gets the apostrophe. To get it right you need to think about who owns what, then make sure that the owner (not the thing owned) gets the apostrophe.

This simple thought process is the secret of getting the position of the apostrophe right.

Remember it doesn’t have to be true ownership. For example, in the phrase, the car’s owner, the car gets the apostrophe because it owns the registered keeper as far as the grammar of that sentence is concerned.

Deciding whether the apostrophe goes before or after the s is simple enough. If the owner is singular (there’s just one of them), the apostrophe goes before the final s.

If the owner consists of several things (plural), the apostrophe comes after the final s.
Here are some more examples to show how it works:

The reporter’s notebook - where the owner is one reporter
The reporters’ notebooks – where there are several reporters

The position of the apostrophe has nothing to do with the number of the things that are owned. It’s the number of owners that’s important.

For example:

The reporter’s pencils – one reporter with lots of pencils in his/her pocket.
The reporters’ room – a team of reporters owning one room.

So the basic rule is simple:

An apostrophe shows possession by being put before the final s of a singular owner, and outside the s of plural owners.

Look at the examples again to check how they follow the rule.

Advanced Apostrophes

If you are feeling confident with the basics, you are ready for the inevitable exceptions to the apostophes rule.

1. Irregular plurals

Some words have irregular plurals. This means they change their vowels instead of adding an s. For example, the plural of man is men, not mans.

So the basic rule for possessive plurals – put the apostrophe outside the final s – needs changing to take account of irregular plurals.

Therefore the amended rule for plurals should be:

For possessive plurals, put the apostrophe at the end of the plural form.

This works both for regular nouns that form plurals with an s and for irregulars that modify their vowels.

For example:

The woman’s desk
the women’s changing room
the mouse’s cage
the mice’s tails

Some words do not change at all to make the plural form.

An example of this is sheep, which does not add an s, even when there are 100 sheep.

If just one sheep has got stuck in a fence, the basic rule applies. The apostrophe goes before the final s.

For example:

The sheep’s foot was trapped in a piece of wire.

But suppose a vet has tested 20 sheep. You would then say …

all the sheep’s blood samples were taken to the laboratory.

This appears to break the rule for plurals; the apostrophe normally goes outside the s on the end of plural owners.

But in fact the basic rule is saying that the apostrophe goes outside the plural form, which normally happens to end in an s but doesn’t in the case of sheep or deer.

Here are three more examples of how to use the apostrophe correctly:

Every spring hundreds of sheep were shorn at Llansannan. The sheep’s fleeces were then sent to Bradford.
(The fleeces of many sheep)

The deer’s coats change colour as they grow older.
(The coats of many deer)

The pollution of the river damaged all the fish’s gills.
(The gills of hundreds of fish)

2. People’s names

Most of us were told at school to put the apostrophe after any name that ends in an s. One referred to James’ motorbike and King Charles’ execution.

This is still strictly correct, but it looks stilted because most people nowadays say James’s motorbike and King Charles’s execution.

This is the way most newspapers write it and most broadcasters say it.

There’s one other obscure but interesting point. If a family has the name Jones, they are the Joneses. There’s no apostrophe, because it’s just a plural. However, when they own something, they need an apostrophe following the rule, outside the s of the plural form as in the line the Joneses’ front garden.

3. Periods of time

One week’s supply
three weeks’ wages.

A day’s leave
14 days’ holiday.

These possessive apostrophes follow the basic rule – the supply of one week, the wages of three weeks, the leave of one day and a holiday of 14 days.