REVISION OF MODAL VERBS-6 --> CAN, COULD, BE ABLE TO
26 / 10 / 2006
REVISION OF MODAL VERBS-6 --> CAN, COULD, BE ABLE TO: meaning and examples
Good morning.
What is the difference between the following sentences?
1) I can speak English.
2) I am able to speak English.
There really is no difference in meaning, but the modal verb can for ability is more usual; so sentence (1) is more common.
However, can, like other modal verbs, doesn't have different forms. Therefore, we often use the "periphrastic" modal verb be able to to express ability in other verb tenses.
3) I haven't been able to practise my English this week because I have been ill. (present perfect)
4) I won't be able to practise my English tomorrow because I have to work. (future)
Etc.
Remember that the past of can is sometimes represented by could.
5) I couldn't understand you when you were speaking to me.
We also have the option of using be able to.
6) I wasn't able to understand you when you were speaking to me.
Could as the past of can for ability is especially common with verbs like see, hear, feel, etc. or to talk about general ability in the past.
7) I couldn't speak English when I was young.
Now we come to the confusing part. In the past many times it is not possible to use could as the modal verb for ability in the past and we must use be able to.
It is necessary to use be able to when the ability being expressed means "manage" (lograr) or overcome a difficulty (supererar una dificultad).
8) Although it was difficult, yesterday I was able to finish the article I was writing.
In example 8 I was able to overcome a difficulty and finish my writing assignment. In this case, could would not work (**Yesterday I could finish the article...**) since could in the past is for general ability (When I was 5 years old I "could" write.)
The negative couldn't is possible in all situations: general ability and overcoming difficulties.
9) Yesterday I couldn't finish the article I was writing. (overcome)
10) When I was 4 years old, I couldn't write. (general ability)
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