MODAL VERBS CAN, COULD AND BE ABLE TO

CAN, COULD AND BE ABLE TO

CAN: is an auxiliary verb, a modal auxiliary verb. We use can to:

• talk about possibility and ability
• make requests
• ask for or give permission

    EXAMPLES:

• She can drive a car.
• John can speak Spanish.
• I cannot hear you. (I can't hear you.)
• Can you hear me?

COULD: is an auxiliary verb, a modal auxiliary verb. 

              We use could to:

• talk about past possibility or ability
• make requests
• to talk about what was possible in the past, what we were able or free to do.

    EXAMPLES:

• I could swim when I was 5 years old.
• My grandmother could speak seven languages.
• When we arrived home, we could not open the door.
• Could you understand what he was saying?

BE ABLE TO: We use be able to to express ability. "Able" is an adjective meaning:having the power, skill or means to do something.

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:

• I would like to be able to speak Chinese.