When is can and could used in a sentence

Although we look at be able to here, it is not a modal verb. It is simply the verb 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 express ability. If we say "I am able to swim", it is like saying "I can swim".

We sometimes use be able to instead of "can" or "could" for ability. Be able to is possible in all tenses - but "can" is possible only in the present and "could" is possible only in the past for ability.

In addition, "can" and "could" have no infinitive form. So we use be able to when we want to use other tenses or the infinitive. EnglishClub : Learn English : Grammar : Verbs : Modals : can, could, be able to can, could, be able to can and could are modal auxiliary verbs. Can you play tennis? Notice that: Can is invariable. There is only one form: can The main verb is always the bare infinitive.

See our more simple notes about Can and Cannot. See our notes about other Modal Verbs. If you found these English Grammar Rules about Can vs Could interesting or useful, let others know about it:.

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Save my name, email, and website in this browser for the next time I comment. While can talks about the possibility of an event in the present situation, could is used to express a slight possibility or the possibility in the past. Both can and could are used to ask for permission and also request something, can is more informal one, which is used when we are talking to our friends, relatives or acquaintances. However, when talking to strangers, we can use could, to ask for permission or request politely.