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Modal verb

The modal verb could

could · never changes

A2Meaning: to be able to, in the past; to be possible; to ask politely · Type: modal

This page for:

Key points to remember

  • Modal: the past of can, or a conditional
  • The same for every person: I/you/he/she/we/they could
  • Negative: could not or couldn't
  • Followed by the base form, without to

Conjugation of the modal verb could

Modal verbs never change: the same form for I / you / he / she / it / we / they, no -s in the 3rd person, and no to before the next verb.

Affirmative

subject + could + base form

  • I could swim when I was five.
  • We could go to the beach tomorrow.

Negative

subject + could not / couldn't

  • I couldn't hear you.
  • She couldn't come.

Question

could + subject + base form?

  • Could you help me?
  • Could she swim?

Could is the past of can (an ability in the past). It is also a polite conditional (more polite than can you) and a way to talk about a possibility.

How to use could

1. Ability in the past

  • I could swim when I was 5.
  • She could read at the age of 4.

2. Polite requests

Could you…? and Could I…? are polite ways to ask for something.

  • Could you help me?
  • Could I borrow your pen?

3. Possibility, conditional

It could rain means that rain is possible. We could go… is a suggestion.

  • It could rain tomorrow.
  • We could go to the cinema.

Common mistakes to avoid

1. Could = past OR conditional

It depends on the context. I could swim at 5 = past (an ability as a child). Could you help me? = polite conditional (a request).

2. I could finish the race yesterday ❌

For a general ability in the past, use could: I could swim as a child ✓. For one success at one moment, use was / were able to: I was able to finish the race ✓.

3. I could to swim ❌

Like all modal verbs, could is followed by the base form, without to: I could swim, not I could to swim.

Going further

Conjugating to could is a key skill in the English contest

Every year, the Big Challenge tests the key English verbs. Register your students so they can check their level in a real contest.

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For teachersReady-made activities to practise to could in class

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Related pages: could

Pages on a similar topic or with a similar use, so you can keep exploring.

Frequently asked questions

What is the difference between can and could?+

Can is for the present: I can swim. Could is for the past (I could swim when I was a child) or for a polite request: Could you help me? is more polite than Can you help me?

Is could always the past of can?+

No. Could has three main uses. (1) The past of can: I could swim at 5 (an ability in the past). (2) A polite request: Could you help me? (3) A possibility: It could rain tomorrow.

Is it could or was able to?+

Use could for a general ability in the past: I could speak English when I was 10. Use was / were able to for one success at one moment: I was able to finish the marathon (I managed to finish it).

What is the negative of could?+

Could not (full form) or couldn't (short form): I couldn't come yesterday.

Is it could you or can you?+

Could you…? is more polite. Can you…? is more direct and informal. With a stranger or a teacher, say Could you…? With a friend, Can you…? is fine.

Updated on 12 November 2026 by the Big Challenge teaching team. Every year, more than 500,000 students across Europe take part in our English contest, created in 1999. Our teaching approach →

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