Can, could, and should in English: ability, requests, and advice

“Can”, “could”, and “should” are modal verbs: they say what the subject is able to do, what someone is asking for, or what someone ought to do. They are simple to use: they stay the same with every subject and are followed by the base form of the verb: “She can drive.”, “Could you help me?”, “You should rest.”

Can: ability and permission

Ability: “I can speak a little English.”, “He can't swim.” Asking for and giving permission: “Can I open the window?” – “Yes, you can.” A common mistake is adding “to” or an “-s”: not “She can to cook” or “She can cooks”, but “She can cook.”

Could: the past and politeness

Use “could” for ability in the past: “I could read when I was five.” In requests, “could” sounds more polite than “can”: “Could you say that again, please?”, “Could I have the bill, please?” It also expresses a possibility: “It could rain later.”

Should: advice

Use “should” to give advice or ask for an opinion: “You should see a doctor.”, “You shouldn't drink coffee at night.”, “What should I do?” To soften advice, start with “I think”: “I think you should ask her.”

A short exercise

Write three things you can do and one thing you can't, using “can/can't”. Say one thing you could do as a child with “could”. Then give two pieces of advice with “should” to a friend who is just starting English.

To keep going, see How to ask questions in English: do, does, and wh- questions and Polite English: asking, thanking, and apologising.

Frequently asked questions

What is the difference between “Can I” and “May I”? Both ask for permission; “May I” is more formal. In everyday speech, “Can I” is common and polite.

Are “should” and “must” the same? No. “Should” gives advice, while “must” states a strong obligation or rule.