Could is a modal verb. It is a helping verb that we usually use with a main verb in a sentence to express ability, possibility, necessity or permission.

Some of the modal verbs are should, would, must, have to, might, etc. Modal verbs give different meanings to the main verbs.

  • I have to get up early tomorrow.(necessity) - have to:modal verb  get up:main verb
  • She might be on holiday. (possibility)
  • You can come in. (permission)

For now, we will only have a look at the use of could for general ability in the past.

How to Use Could

1. When we want to talk about ability in the past, we use could. It is the past   form of can.

  • I could do a 1000-piece puzzle when I was a child.
  • He could play the piano when he was six.
  • She could speak two languages when she was five.
  • My grandfather could drive a tractor when he was young.

2. We use couldn’t when we didn’t have the ability to do something in the past

  • He couldn’t use a fork properly when he was seven.
  • I couldn't speak Spanish when I was 23.
  • Elissa couldn't make cakes till she took baking classes.

How to Form Could 

Positive Sentences (+)

We add could after the subject and use the bare infinitive form of the verb to form positive sentences.

Subject + could + bare infinitive

I could play the guitar when I was 15.

  • Tchaikovsky could read French and German by the age of six.
  • She could tie her shoe laces when she was eight.
  • could cook pasta when I was at the university.

Negative Sentences (-)

We use could not with bare infinitive after the subject to form negative sentences.

The short form of could not is couldn't and we usually use couldn't in negative sentences.

Subject + could not + bare infinitive

He couldn't ride a bike when he was a child.

  • Albert Einstein couldn't talk until he was four years old.
  • I couldn't do Maths until I met Mrs. Campbell.
  • She couldn't pronounce the word 'chocolate' when she was 6.

Questions (?)

We use could before the subject to form questions. 

Could + subject + bare infinitive ?

Could you play chess when you were 10 ?

  • Could you play the guitar when you were sixteen?
  • Could she do ballet when she was five years old?
  • Could they read English story books when they were four?