NI1 - Unit 4B: Modals of obligation

We go on with modals and this lesson deals with obligation. As we saw with CAN, we'll find some problems with tenses and with meanings.
About tenses, remember that MUST is only for present; if you need past tenses you should use HAD TO, but be careful with the negative form which is DIDN'T HAVE TO. Look at the examples:

• I must think about that  ------  I have to think about that  (very similar meaning)
• I had to think about that  ------ I didn't have to think about that

About meaning, there is a slight difference between MUST and HAVE TO. This second is more an external obligation than the other. In negative the difference is bigger like in these exemples:

• I mustn't think about that  -----  it's bad to do it
• I don't have to think about that ----- it's not necessary to do it..

To understand this difference we saw this exercise in class: click here. However, in past tenses we use only DIDN'T HAVE TO with no difference between obligation or not necessary.

If you need more exercises about these modals, you should click here; but if you want to know some more meanings of these modals go to this page which also has exercise.

Although it's not exactly this level, here you are an exdercise to work with SHOULD and SHOULD HAVE ....; click here

As we sere talking about good manners, have a look this video about good manners in English; click here