Can / Be Able To
Listed below are examples and uses of can / could / be able to for ability and permission
Examples | Usage |
He can play tennis well. She is able to speak five languages. They can come on Friday. Jack will be able to come next week. | Use 'can' or 'be able to' to express an ability or possibility NOTE: The future of 'be able to' is 'will be able to |
He could swim when he was five. | Could in the past means the general ability to do something. |
They were able to get tickets for the concert. I was able to finish before 6. I couldn't come last night, sorry. OR I wasn't able to come last night, sorry. | Important: If someone was in the position to do something, or managed to do something, we use 'was/were able to instead of 'could' In the negative,' wasn't able to' OR 'couldn't' are both correct. |
Must / Have To – Mustn’t / Not
Listed below are examples and uses of must / have to / mustn’t / not have to
Examples | Usage |
We have to get up early. She had to work hard yesterday. They will have to arrive early. Does he have to go? | Use 'have to' in the past, present and future to express responsibility or necessity. NOTE: 'have to' is conjugated as a regular verb and therefore requires an auxiliary verb in the question form or negative. |
I must finish this work before I leave. Must you work so hard? | Use 'must' to express something that you or a person feels is necessary. This form is used only in the present and future. |
You don't have to arrive before 8. They didn't have to work so hard. | The negative form of 'have to' expresses the idea that something is not required. It is however, possible if so desired. |
She mustn't use such horrible language. Tom. You mustn't play with fire. | The negative form of 'must' expresses the idea that something is prohibited – this form is very different in meaning than the negative of 'have to'! |
Did the have to leave so early? He had to stay overnight in Dallas. | Important: The past form of 'have to' and 'must' is 'had to'. Must does not exist in the past. |
Use either ‚must‘,’have to‘, ‚mustn’t or ’not have.
Modal Verbs of Probability
Listed below are examples and uses of modal verbs of probability. Modal verbs of probability are used to express an opinion of the speaker based on information that the speaker has. Example: He must be at work, it’s 10 o’clock. In this case, the speaker is 100 % sure that the person is at work based on the speaker’s knowledge that the person in question usually works at during the day.
Examples | Usage |
They must be in Spain by now. She must have done well on the test. | Use 'must' plus the verb when you are 100% (or almost 100%) sure that something is the case. |
She might come this evening. David may invite Jesica to the match. Jack might have gone to France. | Use 'might' or 'may' to express an opinion that you think has a good possibility of being true. |
Jane could be at work. Peter could have arrived late. | Use 'could' to express a possibilty which is one of many. This form is not as strong as 'might' or 'may'. It is just one of a number of possibilities. |
You can't be serious! They can't have worked until late. | Use 'can't' to express an opinion that you are 100% sure is NOT true. Notice that the past form remains 'can't have done' |
Structure
In the present: Subject + Modal + Base Form + Objects
I You He, She We They | must be might be could be can't be | at work. |
In the past: Subject + Modal + Perfect Form + Objects
I You He, She We They | must have left might have left could have left can't have left | early. |