Modal Verbs Summary

Modal Verbs Summary

General structure:                Aff: Subject + Modal Verb (+ Main Verb (base form)).
                                Neg: Subject + Modal Verb + Not (+ Main Verb (base form)).
                                Quest: Modal Verb + Subject (+ Main Verb (base form))?

General Rules: *After a modal verb if you have a main verb always use it in the base form.
                              ** Never use a modal verb after another one.
E.g. I can play the guitar. / I mightn’t come tomorrow. / Would you like? / You should read it.

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1–) Can  (Be Able To)
Aff: I can (do).                                        Infinitive (Ability): Be able to (do).
Neg: I can’t / Cannot (do).                         Future: Will be able to (do).
Quest: Can I (do)?                                Past Simple or General Ability: I Could (do).
Past Neg (all situations): I Couldn’t (do).               Past (Managed Situation): Was/were able to (do).
                                                Present Perfect: I have been able to (do).

1–) Use “CAN” to talk about POSSIBILITY or to say that someone has the ABILITY (or is able) to do something, but usually it’s more natural to use “MAY” or “MIGHT” instead of “can” to talk about Possibility.

E.g. She CAN speak 4 languages. = She has the ability of speaking 4 languages.

        I think Chicago Bulls can win the next NBA season. = I think that it is possible Chicago Bulls wins the next NBA season. (In this case of possibility it’s better to you “MAY” or “MIGHT” instead of can: …Chicago Bulls may/might win…).

2–) Use “COULD” as the PAST SIMPLE of “can” and to talk about the ABILITY SOMEONE HAD.

E.g. When we got to the mountain’s summit we could see dozen of cities. = It was possible to see dozen of cities (Past Simple).

        My grandfather could speak 5 languages = He had the ability of speak 5 languages.

3–) Use “CAN” to ASK SOMETHING, use “COULD” instead of “can” to ask in a politer way.

E.g. Can I have a beer please? (The best choice to ask for something in the commerce).

        Could you help me? (The best choice to ask something for a strange on the street).

4–) Use “CAN’T” to say that YOU THINK SOMETHING IS IMPOSSIBLE. Use “CAN’T HAVE (DONE)” as the past and “CAN’T HAVE BEEN DOING” as the past continuous. Both “COULDN’T HAVE (DONE)” and “COULDN’T HAVE BEEN DOING” are possible ass well for the past, but less sure.

E.g. You’ve had dinner a few moments ago, you can’t be hungry = I think it’s impossible you’re hungry.

She is an incredible player and lost the match? She can’t have been playing seriously. = I think it was impossible that she was playing seriously.

5–) It’s possible to use “BE ABLE TO” instead of “can” to express ABILITY in every situation.

E.g. I am able to play the piano = I can play the piano.

6–) Use “BE ABLE TO” as the INFINITIVE FORM of “can” when it is necessary, like in a perfect tense.

E.g. I haven’t been able to sleep recently. = It hasn’t been possible to sleep recently

(“I haven’t can sleep recently” – It’s wrong – never use a modal verb after another one).

7–) Use “WAS ABLE TO (DO)” to talk about a SPECIFIC SITUATION that someone MANAGED. E.g. The building was on fire but my friend was able to escape safely. = He managed the situation to escape safely. (It wasn’t an ability of escaping, just a particular situation).