Lesson

Can and could

Basic ability and requests

≈ 15 min 8 block(s)

Text

Can and could

Can and could are modal verbs used to talk about ability, permission, possibility and polite requests. 'Can' generally refers to present ability or permission, while 'could' can refer to past ability, polite requests, or conditional possibility.

  • 'Can' = present ability or permission: I can complete the task.
  • 'Could' = past ability or polite request: Could you review this?
  • 'Could' can also be conditional or less certain: It could improve if we invest.

Modals are followed by the base form of the verb (no 'to').

Table

Can vs Could — Quick Reference

Form Use Example
Can + base verb Present ability / permission / general possibility I can finish the report by 5 PM.
Could + base verb Past ability / polite request / conditional possibility When I was younger, I could run ten kilometers.
Could (polite) + subject + base Polite request or offer Could you send the invoice, please?
Be able to Specific completed ability in the past (alternative) I was able to resolve the issue yesterday.

Tip

Key rule: Modal + base verb

Always use the base form of the verb after can or could. Do not add 'to' or inflect the verb.

  • Correct: She can attend the meeting.
  • Incorrect: She can to attend the meeting.
  • Negative: cannot / can't, could not / couldn't
  • Question form: Can you...? Could you...?

Use 'could' for polite requests and for past general ability; use 'was/were able to' for a specific successful action in the past.

Example

Examples in context

I can finish the report by 5 PM.

Could you send the invoice to the client?

When I worked in logistics, I could manage multiple shipments at once.

If you improve the budget, we could hire an additional analyst.

Tip

Common mistakes to avoid

Learners often make predictable errors with can and could. Watch for these:

  • Adding 'to' after can/could (Incorrect: can to; Correct: can + base verb).
  • Using 'can' for past events without context (Prefer 'could' or 'was able to' for past).
  • Adding -s to the modal (Incorrect: he cans).
  • Using could for a single completed success when 'was able to' is clearer.
  • Forming negatives or questions incorrectly (Correct: can't, couldn't; Can you...?, Could you...?)

Double-check time reference and whether the action was a specific past achievement or a general ability.

Quiz

Choose the correct sentence:

Hint: Remember: modal + base verb; no 'to' and no -s on the modal.

Quiz

Complete: _____ you help me with this spreadsheet, please?

Hint: Think about how to make a polite request.

Quiz

Choose the grammatically correct sentence that expresses a specific completed ability in the past:

Hint: Think about single completed past events versus general past ability.

Key Points

GrammarPoint

can

modal verb CEFR A2 //kæn//

Used to express present ability, permission, or general possibility.

I can join the call at 3 PM.

GrammarPoint

could

modal verb CEFR B1 //kʊd//

Used to express past ability, polite requests, or conditional possibility.

Could you review this paragraph?

Expression

be able to

phrase CEFR B1 //biː ˈeɪbəl tuː//

An alternative to modals to express ability, especially for specific past events.

I was able to solve the issue yesterday.

Vocabulary

can't / cannot

modal (negative) CEFR A2 //kɑːnt/ /kəˈnɒt//

Used to express inability or lack of permission.

I can't access the database from home.

Expression

polite request (Could you ...?)

expression CEFR B1 //kʊd juː//

A polite way to ask someone to do something, using 'could'.

Could you send the updated file by noon?

Vocabulary

possibility

noun CEFR B1 //ˌpɒsəˈbɪlɪti//

The state or fact of being possible; 'can' and 'could' are often used to express possibility.

It could take longer than expected.