Could and might

Could = past of can (ability) OR polite request OR possibility.
Might = present/future possibility (less certain than may).

could — past ability

When I was 6, I could swim.

could — polite request

Could you help me, please?

could — possibility

It could rain later.

might — possibility

She might come to the party.

Could for past ability

Past form of "can"

subject + could + base verb → She could swim at age 4.

Positive

I could read when I was 5.

Negative

She couldn't come yesterday.

Question

Could you swim as a child?

For one-time past ability use "was/were able to" or "managed to": "I was able to finish the marathon yesterday" (NOT "I could finish").

Could / might for possibility

Something is possible but not certain

It could rain.

It's possible — maybe 50%.

It might rain.

Also possible — same meaning as could here.

It may rain.

More formal version of "might".

It will rain.

Certain — 100% prediction.

It won't rain.

Certain NOT to happen.

All three (could, might, may) work for possibility. Might is the most common in spoken English.

Could for polite requests

More polite than "can"

Informal

Can you help me?

Can I have a coffee?

Polite

Could you help me, please?

Could I have a coffee?

Use "could" with strangers, at work, in formal situations. Use "can" with friends and family.

Negative forms

couldn't

She couldn't find her keys. (past — inability)

might not

He might not come tonight. (possibility — no contraction "mightn't")

may not

It may not be true. (formal possibility)

"Mightn't" exists but is rare in modern English. Use "might not" in full.

Common mistakes

She could to swim.

→

She could swim.

Modals never take "to"

She might comes.

→

She might come.

Modals never take -s

Yesterday I could finish the marathon.

→

Yesterday I was able to finish the marathon.

specific past achievement → was/were able to

It mights rain later.

→

It might rain later.

might is a modal — never -s

Your turn

Answer out loud — full sentences

Use could and might for possibility, past ability and requests.

What might you do this evening?

What could you do when you were five?

Ask your teacher politely for three things (Could you…?).

The sky is grey. What might happen?

Recap

could

past ability · polite request · possibility

I could swim / Could you help?

might / may

present/future possibility

She might come tonight.

Negative

couldn't · might not · may not

She couldn't come.

All modals

+ base verb, no -s, no "to"

she might come (NOT mights to come)

Practice now →

Could & Might