As an editor, one of the most common things I notice is a person’s confusion over how to use an apostrophe. Some use them anytime an ‘s’ finishes a word, others are hit-and-miss, using them correctly in some instances and not in others, and others still don’t use them at all. So just how should they be used?

As a general rule, an apostrophe is used to indicate a possessive i.e. something is the possession of someone, not to pluralise something. For instance, if a line read “John’s hat is over there” the apostrophe is used because the hat belongs to John. Another example could be “the dog’s bed belongs in that corner”. Again, the bed belongs to the dog; the absence of an apostrophe indicates a plural, like “the photos are all beautiful”. Using an apostrophe in “photos” would change it to being possessive when it should be plural.

In the case of a plural that ends with an ‘s’ (sailors) and possessive, the apostrophe is placed after the end ‘s’. For instance, if a researcher was named Mullins, a sentence could be “Mullins’ study”; if it read “Mullin’s study” the apostrophe would be incorrectly placed, changing the name. (If a plural doesn’t end in an ‘s’, such as ‘children’, an apostrophe is used.)

Apostrophes are also used when two words are merged (known as a contraction), like ‘that’ and ‘is’ to becomes ‘that’s’, or ‘it’ and ‘is’ to become ‘it’s’. This is the exception to the possessive rule.

‘That’s’ always has an apostrophe, it’s never plural. As an example, “that’s the correct temperature”, is “that is the correct temperature”.

However, there are instances where ‘its’ doesn’t require an apostrophe. Understandably, this can be confusing for some writers. An apostrophe isn’t required when it doesn’t mean ‘it is’. For example, “the main selling point of the television is its screen size”. This seems to contradict the rule of the possessive apostrophe, but ‘it’ is a pronoun, which have their own rules for possessives. Other examples are ‘theirs’ and ‘yours’.

The other main offenders people mistakenly use apostrophe is after dates and acronyms/initalisms. If you bought some DVDs, it is plural and so no apostrophe is to be used, just as they aren’t used for other plurals. The same is true with dates, the 1990s saw a number of global changes, not the 1990’s.

Apostrophes can seem confusing, but bear the few simple rules in mind and it’ll become easy.

1) Plurals don’t require an apostrophe, even if they are acronyms or dates.
2) Apostrophes are used as the possessive (John’s, not Johns as this would indicate there is more than one John being mentioned) or or in a contraction
3) Pronouns don’t require apostrophes for the possessive