If you remember these three simple rules, you will avoid mistakes:
1) We use apostrophes to show who something belongs to, e.g. This is Tom’s hat.
2) We also use them for contracted forms, to show that something is missing, e.g. It’s raining.
3) We do not use them for plurals!! If you are in an English-speaking country, you will see many signs in shops and cafés advertising ‘tomato’s’, ‘pizza’s’, ‘sandwich’s’, etc. This is incorrect, and you will lose marks if you do this in an English exam!
These are the main rules to remember, but here is a little more detail:
We also add ’s to plural words that don’t end in ‘s’: women’s books, people’s opinions.
For plurals that do end in ‘s’, we simply put an apostrophe at the end of the word: the animals’ owner, my parents’ house.
For singular words ending in ‘s’, you can add either ’s or – for more formal writing – just the apostrophe: Tess’s phone number, Ben Holmes’s friend, Dickens’ novels.
We often use apostrophes at the end of the names of jobs when we are talking about the place where they work: go to the doctor’s, the greengrocer’s.
In contracted forms, the apostrophe shows where one or more letters has been left out. For example, I’d can mean I had or I would, and they’re means they are. These forms are not suitable for very formal writing, where it is better to write the words in full.
It’s very cold in here.
It’s been a long time since we met.
Who’s coming to the park?
Who’s got the camera?
Look at that chair – its leg has broken.
Whose shoes are these?
Apostrophes may look complicated, but really the rules about their use are quite simple, so I hope this blog has made them clearer. Do leave a comment if you would like help with any other aspect of punctuation, grammar or vocabulary.