Lesson

Can, could and (be) able to

Ability in different tenses

≈ 15 min 8 block(s)

Text

Can, could and (be) able to

This lesson explains how to use the modal verbs can and could, and the phrase be able to, to talk about ability, permission and possibility.

  • Can: present ability or permission (I can speak English; You can go).
  • Could: past ability, polite requests, or present possibility (I could swim when I was small; Could you help me?).
  • Be able to: expresses ability in any tense and replaces can/could where necessary (I was able to finish; She will be able to join).

Table

Can / Could / Be able to — Forms and Uses

Form Use Example
can (present) Present ability or permission I can read reports in English.
could (past / polite request) Past ability; polite requests; possibility When I was 10 I could ride a bike. / Could you review this?
was/were able to (specific past achievement) Successful action in the past (single event) She was able to finish the contract on time.
have/has been able to (present perfect) Ability up to now / experience He has been able to solve several issues this week.
will be able to Future ability You will be able to access the file after approval.
cannot / can't / couldn't Inability or prohibition I can't attend the meeting. / She couldn't log in yesterday.

Tip

Key Rule: When to use be able to

Use be able to when can or could cannot form the tense you need. Use could for past general ability and polite requests.

  • Use can for present ability: I can present the figures tomorrow.
  • Use could for past general ability or polite requests: I could run fast as a child. / Could you send the file?
  • Use be able to for specific past events, perfect tenses, and future forms: She was able to close the deal. / They have been able to reduce costs.

Remember: can has no infinitive or participle — use be able to for perfect tenses.

Example

Examples in context

I can finish the summary by 5 PM.

When he was younger, he could speak three languages.

She was able to resolve the issue before the meeting started.

Could you please review this presentation?

Tip

Common Mistakes

Watch out for these frequent errors when using can, could and be able to.

  • Using can for past achievements: Wrong — I can finish the project yesterday.
  • Confusing could (general past ability) with was/were able to (specific successful action).
  • Omitting to after able: say be able to + verb (not be able + verb).
  • Trying to form perfect tenses with can (use have/has been able to instead).
  • Using could to mean present ability (could usually implies past or hypothetical).

Focus on tense and whether the ability refers to a specific action or a general ability.

Quiz

Choose the correct sentence:

Hint: Think about a single completed action in the past.

Quiz

Complete: _____ send the file last week?

Hint: Think about forming a past-tense question about success.

Quiz

Which sentence is the most polite request?

Hint: Choose the modal verb typically used for polite questions.

Key Points

GrammarPoint

can

modal verb CEFR A2 //kæn//

used to express present ability or permission

I can join the call at 10.

GrammarPoint

could

modal verb CEFR B1 //kʊd//

used for past ability, polite requests, or hypothetical situations

Could you approve the budget, please?

GrammarPoint

be able to

phrase (modal equivalent) CEFR B1 //biː ˈeɪbəl tuː//

used to express ability in any tense; replaces can/could when needed

She has been able to negotiate better terms.

Vocabulary

inability

noun CEFR B2 //ˌɪnəˈbɪləti//

the state of not being able to do something

His inability to attend delayed the decision.

Vocabulary

permission

noun CEFR A2 //pəˈmɪʃən//

authorization to do something

Can I have permission to access the server?

Vocabulary

achievement

noun CEFR B2 //əˈtʃiːvmənt//

a completed task or success, often after effort

Securing the client contract was a major achievement for the team.