The Possessive Apostrophe

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Possessive apostrophes are used to show ownership or association, such as "Mary's book" or "Tom's dance club." Its use is the same in American and British English. However, the rules that govern its use can be somewhat complicated.

I'll start by describing the "official" rules and then follow up with a quick guide, which, although not always grammatically correct, does provide the reader with a smooth reading experience.

The 'Official' Rules

It is very important to remember that only nouns use possessive apostrophes. Adding possessive apostrophes to pronouns is a common mistake:

Claire has a new car. It's colour is red.

"It's" is a contraction of "It is".

Two correct uses of this of this pronoun are:

Claire has a new car. Its colour is red.

or

Claire has a new car. It's red.

The rules for using possessive apostrophes vary depending on whether the nouns end in an "s" and are singular, plural or proper nouns.

Singular Nouns

Most singular nouns add "apostrophe-s":

• The footballer's injury
• The dog's bone
• The bird's nest

Plural Nouns

For plural nouns that end in "s", only add an apostrophe:

• The footballers' injury
• The dogs' bones
• The birds' nest

Proper Nouns

Add "apostrophe-s" if a singular proper noun doesn't end in "s". Opinions vary on how to handle possessive apostrophes when singular proper nouns end in "s":

• Add an apostrophe,
• Add "apostrophe-s",
• Add either an apostrophe or "apostrophe-s", depending on which sounds the best.

Whichever style you decide to use, it's important to be consistent within the same document. The flowchart shown below adds an apostrophe if the proper noun ends in "s".

Plural proper nouns are treated in the same way as singular nouns.

A flowchart of the possessive apostrophe rules

A Simple Approach

If, like me, you find the above approach too complicated, you might be interested in the following method:

• If the word ends in "s", add an apostrophe.
• If the word doesn't end in "s", add "apostrophe-s".

Here are some examples:

• The footballer's injury.
• The footballers' changing room.
• The children's playground.
• John Fowles' novel

Like the above flowchart, this method doesn't always produce the best result with singular proper nouns that end in "s".

For example, "Thomas' book" doesn't feel right, so I would use "Thomas's book". On the other hand, "John Fowles's novel" doesn't sound right.

As a general guideline, I use an apostrophe if the "s" sounds like a "z" and "apostrophe-s" if the "s" sounds like an "s".

The following flowchart summarises this simpler method:

A simple possessive apostrophe flowchart

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