Could and couldn’t are modal
auxiliary verbs. Could and couldn’t are the past tense forms of can and can’t.
We use could
and couldn’t to:
- talk about past possibility or ability
- make
requests
Structure
subject + could/couldn’t
+ main verb
The main verb is
always the infinitive without "to".
subject
|
auxiliary verb
|
main verb
|
|
+
|
My grandmother
|
could
|
swim.
|
-
|
She
|
could not
|
walk.
|
couldn't
|
|||
?
|
Could
|
your grandmother
|
swim?
|
Uses
Past Possibility or Ability
We use could to
talk about what was possible in the past, what we were able or free to do:
- I could speak English when I was
5 years old.
- My grandmother could swim.
- When we arrived home, we couldn't open the door.
- Could you
understand what he was saying?
We use could (positive)
and couldn't (negative) for general ability in the past. But
when we talk about one special occasion in the past, we use be able to (positive)
and couldn't (negative).
Past
|
||
General
|
Specific Occasion
|
|
+
|
My grandmother could
speak Spanish.
|
A man fell into the river
yesterday. The police were able to save him.
|
-
|
My grandmother couldn't speak
Spanish.
|
A man fell into the river
yesterday. The police couldn't save him.
|
Requests
We often use could in
a question to ask somebody to do something. The use of could in
this way is fairly polite (formal):
- Could you
tell me where the bank is, please?
- Could you
send me a catalogue, please?
