Can & Can't: Ability, Permission, Requests

A1 Grammar

1. Simple explanation

Use 'can' to say you are able to do something — that you have the skill or the possibility: 'I can swim.' Use 'can't' (the short form of 'cannot') when you are not able, or when something is not allowed — not permitted by the rules: 'You can't park here.' After can and can't, always use the base verb — the verb's first, simplest shape, like swim, go, sing — with no 'to' and no -s: 'She can sing,' never 'She can sings.'

2. Detailed explanation

Start from zero. A verb is a word that shows an action (swim, run, speak) or a state (be, know). The base form of a verb is its simplest, dictionary shape, with nothing added: swim, run, speak. This lesson teaches a helper word: 'can.' Can is called a modal verb — 'modal' is the grammar name for a small group of helper verbs (can, could, must, should) that add an idea like ability or permission. Can is never a full action alone; it needs a main verb after it: in 'I can swim,' swim is the action, can adds 'I am able to.' Can has three big jobs: ability, permission, and requests.

Job one — ability: something your body or brain knows how to do. 'She can speak three languages.' The opposite, can't (= cannot), means 'not able to': 'I can't swim.' Job two — permission: asking if something is OK. 'Can I sit here?' means 'Is it allowed?' Saying something is not allowed: 'You can't smoke here.' Job three — polite requests: 'Can you help me, please?' You are not asking about ability — you are asking the person to do something, in a friendly way. The word 'please' makes any request softer and more polite.

Now the grammar — and here is the good news: can never changes. It is 'can' for every subject: I, you, he, she, it, we, they. It never takes an -s ('he can,' never 'he cans'), and the verb after it is always the plain base form: no 'to' ('can go'), no -s ('she can sing,' never 'she can sings'), no -ing. Let's take sentences apart, word by word. 'She can speak English': She (the person) + can (the helper — ability) + speak (the base verb) + English (what she can speak). 'Can I sit here?': Can (the helper, at the front to make a question) + I (the person) + sit (the base verb) + here (this place). 'He can't drive': He + can't (can + not) + drive (the base verb). Questions never need 'do' or 'does,' and short answers repeat can: 'Can you swim?' — 'Yes, I can.'

The hardest part of 'can' is not grammar — it is listening. In the middle of a sentence, Americans say 'can' quickly and weakly — it shrinks to a soft 'kuhn': 'I kuhn do it' means 'I CAN do it.' But 'can't' is the opposite: strong, clear, and ending with a sharp T sound: 'I CAN'T do it.' So do not listen for the whole word — listen for the strength: weak = can (able), strong with a T = can't (not able).

3. Formula / structure

negative:

positive:

question:

Step by step — how to build a sentence:

4. When to use it

• Ability — skills and things you know how to do: 'I can ride a bike.'
• Permission — asking if something is OK: 'Can I open the window?'
• Rules — saying what is not allowed: 'You can't take photos in the museum.'
• Polite requests: 'Can you pass the salt, please?'
• Possibility in general: 'It can be very cold here in January.'
• Offers of help: 'Can I help you?' — the classic first line in a store.

5. When NOT to use it

• Never add -s: ✗ 'He cans swim' → ✓ 'He can swim.' (can is the same for every subject)
• Never use 'to' after can: ✗ 'I can to drive' → ✓ 'I can drive.'
• Never use do/does with can: ✗ 'Does she can dance?' → ✓ 'Can she dance?'
• Don't answer 'Yes, I do' to a can-question — the short answer repeats can: 'Can you swim?' — 'Yes, I can.'

6. Positive examples

• I can swim very well.
• She can speak English and Spanish.
• We can see the sea from our window.
• He can play the piano beautifully.
• Birds can fly, but penguins can't.
• You can use my phone if you need to.
• My little brother can count to one hundred.
• The baby can walk now.
• You can buy tickets online.
• We can hear the music from here.
• She can type very fast.

7. Negative examples

• I can't hear you — please speak up.
• He can't drive. He's only ten years old.
• You can't park here. It's not allowed.
• We can't come to the party on Saturday.
• She can't sleep with all this noise.

8. Questions

• Can you swim?
• Can I sit here, please?
• Can he speak English?
• Can you help me with this bag?
• Can we go home now?
• Can I have a coffee, please?

9. Short answers

• Yes, I can. / No, I can't.
• Yes, she can. / No, she can't.
• Yes, you can. (giving permission)
• No, you can't. (refusing permission — soften it with 'Sorry, …')
• Yes, we can. / No, we can't.

10. Common mistakes

11. American English notes

12. Similar grammar — comparison

13. Natural spoken English

• 'Can I help you?' — the first thing you hear in an American store
• 'Sure, I can do that.' — agreeing to a request at work
• 'Sorry, I can't. I have to work tonight.' — a soft, polite refusal
• 'Can you say that again, please?' — the most useful sentence in any English class
• 'You can do it!' — encouragement; here 'can' is strong and stressed
• 'I can't wait!' — it means 'I'm very excited!', not 'waiting is impossible'

14. Real-life examples

• At a restaurant: 'Can I have the menu, please?' (polite request)
• At the airport: 'You can't take water through security.' (a rule)
• In class: 'Can I go to the bathroom, please?' (permission)
• On the phone: 'Sorry, I can't hear you — the music is loud.' (ability, now)
• At work: 'Can you finish this today?' — 'Yes, I can.' (request + short answer)
• Reading signs: 'You can pay by card here.' (permission/possibility)

15. Mini dialogue

16. Summary

17. Practice exercises

Warm up with the first questions, then take the full quiz — every answer has a detailed explanation (parts 19–20 of this lesson: answer key + explanations live inside the quiz feedback).

18. The full quiz

50 questions, mixed formats, in difficulty order: easy → medium → intermediate → challenging → advanced.

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