Can and may, both words leave the writers and speakers confused about which word to use and when. The correct use of these words sometimes cannot be determined as easily as we imagine, because in some situations both can be used, but the difference is in their preferable use.
When to Use Can
Can is an auxiliary verb (helping verb). It is used to express the physical and mental ability.
- I can sing. (ability)
- She can dance. (ability)
- Can he lift 100 kgs? (ability)
When to Use May
May is also an auxiliary verb. It is used to ask or grant permission.
- May I come in? (asking for permission)
- May I make a call from your phone? (asking for permission)
- You may go now. (granting permission)
Are can and may interchangeable?
People often get confused when these verbs are used to ask/grant permission. For example, which sentence in your opinion is more appropriate?
- Can I use your computer, please?
- May I use your computer, please?
It is a widespread view that we cannot use can to ask for a permission rather it should be used to show ability or capability. For example,
- Can you sing?
- Can she speak English?
But in standard English, use of can for permission is not incorrect, the only difference between them is one is more polite than the other. In formal situations, use of may is more appropriate. For example,
- Can I speak to Mr. Ali, please?
- May I speak to Mr. Ali, please?
In the above situation, use of may sounds more polite.