• 3-minute read
• 6th November 2018

Word Choice: Can, May or Could?

The terms ‘can’, ‘may’ and ‘could’ are often used interchangeably. But is this correct? Well, whether there is a difference between these words depends on how they are used. So read on to find out exactly why English has so many terms for expressing possibility and making requests.

Expressing Possibilities

‘Can’, ‘may’ and ‘could’ are all modal verbs used to express the possibility of something. For instance, to suggest a strong possibility of something, we might use the word ‘can’:

Vitamin C can boost your immune system.

Using ‘can’ in this sentence suggests not just a possibility, but a likelihood. However, if we were less certain, we would use ‘may’ or ‘could’ instead:

Vitamin C may boost your immune system.

Vitamin C could boost your immune system.

The difference between these terms here, then, is how strong a claim we want to make. We can also make a stronger claim by using the verb ‘will’ or not using a modal verb at all:

Vitamin C will boost your immune system.

Vitamin C boosts your immune system.

Both of these suggest that vitamin C is certain to improve your immune system, not that it is simply likely or possible that it will do so.

Making Requests and Granting Permission

The other situation in which ‘can’, ‘may’ and ‘could’ can all be used is making a request. In this case, the only difference between these terms is how formal they are. For example:

May I have a lemon? = Very formal

Could I have a lemon? = Less formal

Can I have a lemon?  = Informal

All of these sentences are ways of asking for a lemon, but the first is politer and more formal than the others. Nevertheless, in everyday language where formality isn’t an issue, ‘can’ is the most common of these terms. You will only need to use ‘may’ instead if you are making a formal request.

If we are granting permission for something, meanwhile, we can use either ‘can’ or ‘may’. And as with making a request, ‘may’ is much more formal than ‘can’ in this context.

Summary: Can, May or Could?

Whether these terms are interchangeable depends on how they are used. When discussing whether something is possible, for example, we would use ‘can’ to express a strong probability or general truth. ‘May’ and ‘could’, by comparison, suggest we are less certain about something.

But if we are asking for permission, these words mean the same thing. However, if you want to be formal, you should use ‘may’ instead of ‘could’ or ‘can’, as this is the traditional usage.

And if you need any help ensuring that you use the right words in the right places, give our proofreading service a try by uploading a 500-word sample of your writing for free today.