Could and Can: ability and permission
Could for past ability; can for permission.
English uses two modal verbs to talk about ability and permission at this level: could and can. These have two clearly different jobs, so it is important not to mix them up. FIRST JOB — PAST ABILITY: Use could / couldn't to say what someone was or was not able to do at an earlier time. 'She could swim when she was five.' (she had the skill in the past) and 'I couldn't ride a bike last year.' (I did not have the skill last year). In questions, could moves to the front of the sentence: 'Could you speak English in 2020?' As a reference point, remember that can / can't describe PRESENT ability: 'I can swim now.' compares directly with the past sentence 'I could swim when I was five.' SECOND JOB — PERMISSION: Use can / can't and Can I…? to ask for, give, and refuse permission NOW. 'Can I open the window?' asks if something is allowed. 'You can go now.' gives permission. 'You can't use your phone in class.' refuses permission. 'Can we leave early?' asks for a group. A more polite way to ask for permission is with may (or even could, in very polite requests), but at this level the form we practise and test for permission is can. Do not confuse the two jobs: ability describes a skill or capacity a person has ('I can swim' = I know how to swim), while permission describes what is allowed ('You can go' = you are allowed to go). The same test applies to the past form: 'She could swim' talks only about a past skill, never about permission that was granted.
Key terms
| Form | Pattern | Example |
|---|---|---|
| Affirmative | could + base verb | She could swim when she was five. |
| Negative | couldn't (could not) + base verb | I couldn't ride a bike last year. |
| Question | Could + subject + base verb…? | Could you speak English in 2020? |
| Short answer (positive) | Yes, + subject + could. | Yes, she could. |
| Short answer (negative) | No, + subject + couldn't. | No, we couldn't. |
Use could/couldn't to talk about a skill or capacity someone had (or did not have) in the past — never for permission at this level.
| Function | Pattern | Example |
|---|---|---|
| Asking permission | Can + subject + base verb…? | Can I open the window? |
| Giving permission | subject + can + base verb | You can go now. |
| Refusing permission | subject + can't + base verb | You can't use your phone in class. |
| Asking permission (group) | Can we + base verb…? | Can we leave early? |
| Polite alternative | May I…? (more formal, only mentioned) | May I open the window, please? |
Use can/can't (and Can I…?) to talk about what is allowed right now. May is a more polite alternative you may see, but can is the form we practise here.
| Use | Time | Example | Meaning |
|---|---|---|---|
| Past ability | past | She could swim at five. | She had the skill in the past. |
| Present ability | present | I can swim now. | I have the skill now. |
| Permission (asking) | present | Can I open the window? | Asking if it's allowed right now. |
| Permission (refusing) | present | You can't use your phone in class. | It's not allowed right now. |
The same words (can/could) can describe ability OR permission — look at the meaning of the whole sentence to decide which one is being used.
- 1Start: Statement: 'You could speak English in 2020.'
- 2Step 1: Move 'could' to the front: Could you speak English in 2020?
- 3Step 2: Answer positively: Yes, I could. (Do NOT say 'Yes, could I.' — the subject comes after 'Yes/No'.)
- 4Step 3: Answer negatively: No, I couldn't. (Short form of 'could not'.)
- 1Identify the situation: You want to open the window in class.
- 2Step 1: Ask for permission: Can I open the window?
- 3Step 2: Giving permission: Yes, you can. / Yes, of course.
- 4Step 3: Refusing permission: No, you can't. It's cold outside.
Do NOT say 'I can swim when I was five.' Time words like 'when I was five' show the past, so use 'could': 'I could swim when I was five.'
Do NOT say 'Can I opened the window?' — after 'can' or 'could' always use the base form of the verb: 'Can I open the window?' not 'opened' or 'opening'.
Don't confuse ability and permission! 'I can swim' = I have the skill (ability). 'Can I swim in this pool?' = Am I allowed? (permission). Read the whole sentence carefully to see which meaning is being tested.
'Could I…?' and 'May I…?' are also used in real English as more polite ways to ask for permission right NOW (not about the past). In this unit we focus on can/can't for permission and could/couldn't for past ability.
Rules
- 1Use could / couldn't for PAST ability — what someone was or was not able to do before now: 'He could run fast when he was young.' 'They couldn't read yet at age four.'
- 2Use can / can't for PRESENT ability as a reference point, to compare with the past: 'I can swim now' (present) vs 'I could swim at five' (past).
- 3Use can / can't and Can I…? / Can we…? for PERMISSION — asking, giving, and refusing what is allowed NOW: 'Can I go?' 'You can go.' 'You can't go.'
- 4Could makes past-ability questions ('Could you speak English in 2020?'); can makes permission questions ('Can I open the window?'). Do not use could to ask for permission at this level.
- 5May is a more polite way to ask for permission ('May I…?'), but can is the form we practise here; do not confuse can/could with must/have to (obligation) or should (advice) — those are different topics.
Practice
10 easy · 10 medium · 10 hard
10 random questions per test