Топик: Сравнительные степени прилагательных и наречий (Comparison) Модальные глаголы (Modal Verbs) Цепочки существительных (Атрибутивная, номинативная группа) (Chains of nouns)
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.
could: 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?
Be able to
Although we look at be able to here, it is not a modal verb. It is simply the verb "to be" plus an adjective (able) followed by the infinitive. We look at "be able to" here because we sometimes use it instead of "can" and "could". We use "be able to":
-
to talk about ability
Structure of Be able to
The structure of be able to is:
subject + be + able + infinitive
|
subject |
be |
able |
infinitive | |
| + | I |
am |
able |
to drive. |
| - | She |
is not |
able |
to drive. |
|
isn't | ||||
| ? |
Are | you |
able |
to drive? |
Notice that be able to is possible in all tenses, for example:
-
I was able to drive...
-
I will be able to drive...
-
I have been able to drive...
Notice too that be able to has an infinitive form: