GRAMMAR - MODAL VERBS
EXPRESSING CERTAINTY (ISTOTA)
- when we are sure about something we use MUST, CAN‘T and COULDN‘T
1. for present situations a modal verb is followed by the infinitive without “to“ (go) or the continuous infinitive (be going)
infinitive:
I have been running for forty minutes. - You MUST BE tired. – I am sure you are tired.
He CAN’T/COULDN‘T BE ill. I saw him in the morning. – I am sure he isn’t ill.
continuous infinitive:
Where is our mum? – She MUST BE COOKING.
Where is our dad? / He CAN’T/COULDN’T BE WATCHING TV. It is turned off.
2. for past situations a modal verb is followed by the perfect infinitive without “to” (have gone) or the perfect continuous infinitive (have been cooking)
perfect infinitive:
I don’t have my keys. I MUST HAVE LOST them. (in the past)
I CAN’T/COULDN’T HAVE LOST my keys at school because I wasn’t there yesterday. (in the past)
perfect continuous infinitive:
Her test is the best in the class. She MUST HAVE BEEN REVISING for ages. (in the past)
Her test is the worst in the class. She CAN’T/COULDN’T HAVE BEEN REVISING for it. (in the past)
EXPRESSING POSSIBILITY
- when we think that something is possible, we use MAY, MAY NOT, MIGHT, MIGHT NOT, COULD (not couldn’t since it expresses certainty)
1. for present situations a modal verb is followed by the infinitive without “to“ (go) or the continuous infinitive (be going)
infinitive:
He is not at school. – He MAY/MIGHT/COULD BE ill. – It is possible but I don’t know it for sure.
His car isn’t here. – He MAY NOT/MIGHT NOT be here right now. – It is possible that he isn’t here. (compare with He couldn’t be here. – couldn’t expresses certainty so I am sure he is not here.)
continuous infinitive:
He MAY/MIGHT/COULD BE TELLING the truth. - It is possible that he is telling the truth.
He MAY NOT/MIGHT NOT BE TELLING the truth. - It is possible that he is not telling the truth.
2. for past situations a modal verb is followed by the perfect infinitive without “to” (have gone) or the perfect continuous infinitive (have been cooking)
perfect infinitive:
I MAY/MIGHT/COULD HAVE LEFT my keys at school yesterday. - It is possible that I left my keys there.
I MAY NOT/MIGHT NOT HAVE LEFT my keys at school. – It is possible that I left my keys somewhere else and not at school. (compare with I couldn’t have left my keys at school. – couldn’t expresses certainty so I am sure that my keys are somewhere else and not at school)
perfect continuous infinitive:
Her last test is better than the previous one. She MAY/MIGHT/COULD HAVE BEEN REVISING for it last week. – It is possible that she was revising for the test.
Her last test is worse than the previous one. She MAY NOT/MIGHT NOT HAVE BEEN REVISING for it. – It is possible that she wasn’t revising for it. (compare with She couldn’t have been revising. – couldn’t expresses certainty so I am sure that she wasn’t revising at all.)