• 3-minute read
  • 21st December 2019

Word Choice: Can, May, or Could?

The terms “can,” “may,” and “could” are often used interchangeably. But is this correct? Well, the difference between these words is often a matter of formality, but it depends on how you use them. Read on to find out 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. To suggest a strong possibility, for instance, we use “can”:

Vitamin C can boost your immune system.

Using “can” in this way 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 lies in 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. For example:

Vitamin C will boost your immune system.

Vitamin C boosts your immune system.

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

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Making Requests and Granting Permission

The other situation in which “can,” “may,” and “could” can all be used is to make a request. In this case, the only difference is between how formal they are. For example, we could use these terms as follows:

May I have a lemon? = Very formal

Could I have a lemon? = Less formal

Can I have a lemon?  = Informal

All these sentences are ways of asking for a lemon, but the first is politer and more formal than the others. In everyday language where formality isn’t an issue, “can” is the most common of these terms. But you may want to use “may” if you’re making a very formal request.

Since you asked so nicely.
Since you asked so nicely.

If we are granting permission for something, meanwhile, we can use either “can” or “may.” As with making a request, “may” is much more formal than “can” in this context, but they essentially mean the same.

Summary: Can, May or Could?

Whether these terms are interchangeable depends on how you use them:

  • Discussing a Possibility: “Can” suggests a strong possibility or a general truth. “May” and “could” suggest we are less certain about something.
  • Asking for Permission: You can use all three words to ask for permission. To be formal, though, you should use “may” instead of “could” or “can.”

And if you need any more help ensuring you use the right words in the right places, try our proofreading service for free today!

Comments (8)
14th November 2020 at 06:00
Thank you, the explanation was most helpful
    26th August 2021 at 00:59
    Nice 👍🏻✌🏻
      Sakhile Nomankantshu
      20th December 2022 at 11:39
      I'm thankful for these wondrous explanations. It's advantageous to me. It was very difficult for me to know how these modal verbs differ.
      22nd December 2022 at 12:55
      Hi, Sakhile. You’re very welcome indeed! I’m so glad this article helped you.
Grammah Leigh
3rd March 2022 at 16:44
"May" is only used for asking permission in the first person; "May I...". if 'may' is followed by 'you', it's incorrect usage.
    4th March 2022 at 10:36
    Hi, Leigh. That isn't technically true: you can use "may you" as a formal way of wishing something for someone (e.g., "May you have a happy day ahead"). This would sound quite unusual in modern English, but it isn't strictly wrong. It is correct to say that you wouldn't use "May you..." to ask for permission, but that's because you can't ask for permission in the second person: rather, you can ask if someone is able to do something ("Can you...?"), whether they would be willing to do something ("Would you...?"), or if they intend to do something ("Will you...?"). Usually, when asking for permission, it will be for yourself ("May I...?" and so on) or on behalf of someone else ("May he/she/they...?" and similar). Hope that clarifies things slightly!
4th March 2022 at 08:35
Which one is true '' Can i go to school? '' or '' May i go to school? ''?
    4th March 2022 at 10:29
    Hi, Gulnur. Both of those are grammatical. As we explain in the post, the difference in modern English is mostly one of formality, with "may" more formal than "can."

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