Can, could, and should in English: ability, requests, and advice
“Can” is for ability and permission, “could” for past ability and polite requests, and “should” for advice. All three stay the same with every subject and are followed by the base form of the verb. Examples and a short exercise.
By Aslıgül Aşkın,
Guide: Grammar. Main post: English tenses: all of them in one table
“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.
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