B2 Grammar: Modal verbs to express certainty and possibility

Modal verbs to express certainty and possibility

To express certainty about the present	·        Use must: She’s been in over 15 films, so she must be very well known. Note: we usually have a good reason for expressing this certainty, e.g. She’s been in over 15 films. ·        Use can’t or couldn’t for the negative (not mustn’t). You can’t be tired. You’ve just got out of bed! Mark couldn’t be coming to the party – he’s on holiday in America at the moment.
To express certainty about the past	·        Use must have + past participle: You have a very big part in the play. It must have taken you ages to learn all the lines. ·        Use can’t have and couldn’t have + past participle for the negative: She can’t have left her glasses at home – I saw her wearing them on the bus. She couldn’t have stolen the money because she’s far too honest!
To express possibility about the present or future	·        Use may, might or could: I may come and visit you next summer. We might go to the cinema this evening if we finish all our work in time. We’d better go out for a walk now because it could rain later. ·        Use may not and might not (not mayn’t or mightn’t) for the negative (not can’t or couldn’t which express certainty): Frankie is looking very pale. He may not be very well. Don’t cook any dinner for me because I might not be back in time.
To express possibility about the past	·        Use may have, might have, could have, may not have, might not have + past participle: It’s unlike Sally to be late. She may have overslept, or she might not have remembered the appointment.

B2 Grammar: Verbs expressing ability

Expressing ability

To say someone has an ability, use can, can’t, could, couldn’t, be able to and manage.

·    In the present, use:

can or am / is/ are able to for things which are possible: Francesca can speak five languages, but she can’t speak Russian. She’s able to play the piano but she isn’t able to play the violin.

can’t or am not / isn’t / aren’t able to for things which are not possible (see examples above).

Note: We usually use can and can’t when speaking because they are shorter.

·    In the past, use:

could only when you are speaking in general: When I was a child, I could read without glasses. (not I was able to read without glasses).

was / were able to when you are speaking about one particular occasion: Dad didn’t have any money on him, but fortunately he was able to use his credit card to pay the bill. (not he could use his credit card to pay the bill).

couldn’t and wasn’t / weren’t able to when you are speaking in general and also when you are speaking about one particular occasion: Pascual wasn’t able to / couldn’t do all the questions in the maths exam. Olga couldn’t / wasn’t able to ride a bike till she was 18.