Impersonal verbs for must and can
In English, must and can go with a person: I must, she can. Arabic uses two verbs that never change. يجب means it is necessary and يمكن means it is possible. They stay in this one form, and the person is shown by a preposition instead.
يجب على — must
Put the person after على (on): the duty is on them. Then add أن and a present-tense verb in the subjunctive.
With a pronoun, على takes the attached ending: عليّ، عليك، عليه، عليها، علينا، عليكم، عليكما، عليهم.
يمكن لـ — can
يمكن works the same way with لـ (for): it is possible for the children to see.
You will also meet the pronoun attached to يمكن itself, as in يمكنك أن…. It means the same thing.
Cannot
Put لا in front of يمكن: لا يمكن means cannot.
| Arabic | word for word | meaning |
|---|
| يجب على المهرج أن يجلس | it is necessary on the clown that he sits | the clown must sit |
| يجب علينا أن ننتبه | it is necessary on us that we pay attention | we must pay attention |
| يمكن للأطفال أن يروا | it is possible for the children that they see | the children can see |
| لا يمكن للساحر أن يقف | it is not possible for the magician that he stands | the magician cannot stand |
The verb after أن
يجب and يمكن never change, but the verb after أن agrees with the person: علينا → ننتبه, عليكم → تتبعوا, عليكِ → تنتبهي. Because it follows أن, it is in the subjunctive, so the plural and the feminine lose their final ن.
Without يجب
You can also drop يجب and keep only على + the pronoun: عليك أن تنتبه means you have to pay attention, علينا أن نجلس we have to sit. Two more frames say the same things more softly: ينبغي أن (should, ought to) and من الممكن أن (it is possible that). After all of them the verb is in the subjunctive.
| frame | meaning |
|---|
| يجب عليك أن تنتبه | you must pay attention |
| عليك أن تنتبه | you have to pay attention |
| ينبغي أن تنتبه | you should pay attention |
| يمكنك أن تنتبه | you can pay attention |
| من الممكن أن يتأخر | he might be late |
