MODAL VERBS Possibility
e.g. I can go to the party Could
+ e.g. I could go to the party if he invited me
Present e.g. I can go to the party. Past (only negative)* e.g. I couldn't go to the party yesterday
e.g. I can drive e.g. Can I go to the e.g. Can you open the e.g. Can I help a car.
Past polite e.g. I could swim e.g. Could I go to when I was 12.
e.g. I may visit John (Maybe I
will visit John)
the toilet, please?
+ polite e.g. May I go to the
e.g. Could you open
e.g. Could I
the door, please?
+ polite e.g. May I ask you to
open the door, please?
+ polite e.g. May I help you?
e.g. I might visit John (Maybe
I'll visit John, but it isn't likely)
BE ABLE TO. It expresses ability and possibility in all tenses. It stands for “CAN” in all those tenses it – being a modal verb – lacks. Present simple → I am able to help you know. Present perfect → I have been able to help John recently. Past Simple → I was able to help John yesterday.
Past perfect → He had been able to help him before that moment. Future → I will be able to help tomorrow. Future perfect → He will have been able to help you by then
* In general, CAN, COULD, MAY & MIGHT express possibility only in the present, and “be able to” is used to express possibility in any other tense, but “couldn't” is often used to express possibility in the past when the sentence is negative, so that “couldn't” and “wasn't/weren't able to” mean the same when talking about the past: e.g. I couldn't open the bottle = I wasn't able to open the bottle - Must
- Obligation → You must respect your elders. - Logical deduction → That noise must be the clock.
- Have to Obligation (all tenses) You have to study hard this year. - Mustn’t Prohibition You mustn’t drink alcohol - Don’t/Doesn’t have to Lack of obligation You don’t have to hurry. We are in time.
- Needn’t Lack of necessity (= don’t have to) e.g. You needn’t shout, I’m not deaf.
- Request Would you mind explaining this again? - Would - Offer Would you like a cup of tea? - Usual action in the past I would play all day with my friends - Shall Offers Shall I help you with the bags? - Should Opinion / Advice You should be nice to your classmates
Must have + participle Could have + participle
Logical conclusion that something happened in the past The possibility for something to happen existed, but finally it didn’t happen
Couldn’t have + participle
The impossibility for something to happen in the past.
May / Might have + participle
Guess about the past; the possibility that something happened.
Should have + participle
Regret about something that didn’t happen in the past.
Shouldn’t have + participle
Regret about something that happened in the past.
Needn’t have + participle
Unnecessary action that happened in the past.
He left some time ago, so he must have arrived home by now. He could have taken the bus, but he didn’t, so he was late. He is not the murderer. It was too early. He couldn’t have arrived to the crime scene before the time of the victim’s death
We haven’t seen their car for days. They may have bought a new car (It is possible that they have bought a new car) We didn’t study hard enough for the test. We should have studied harder. We went our instead of studying. We shouldn’t have gone out. We bought an expensive bottle of wine, but our guests didn’t drink alcohol. We needn’t have bought the wine.