Lesson 9 – Step 3 – Obligations, suggestions, and prohibitions

Goal

It is time to learn three very useful concepts. How to give orders, how to give advice and how to forbid things. With that goal in mind, we will learn about some modals and verbs that convey these ideas.

You can watch the video or go straight to the written explanation. You decide! Once you’ve finished, you can move to step 4.

Language Discovery

Look at the words in blue in the text on step 1. What do they have in common?

•  They convey obligation.

Look at the words in green in the text on step 1. What do they have in common?

•  They convey suggestion.

Obligation

We use have to and must to express obligation or strong recommendation. They have a similar meaning, but there are small differences:

• must: internal, personal obligation, something we impose to ourselves.
• have to : general,  external obligation, something others expect us to do. 

Look at these examples. Notice that verbs after have to and must are in the infinitive.

• You will have to take a covid test.
• You didn’t have to do that.
• Do I have to take that medicine?
• I  must take care of myself.
• You mustn’t smoke in this place.
• Must I be vaccinated to fly?

Important

Mustn’t and don’t have to are VERY different in meaning.

• We use the don’t have to, to express that something is not necessary.
• We use the mustn’t, to express a prohibition. 

Suggestions

We use should and ought to, to give advice or an opinion.

We use had better to give strong advice that when not followed, might have bad consequences.

• You should take an aspirin.
• You shouldn’t go out with your hair wet.
• If you have a headache you ought to take an aspirin.
• It’s about to rain! You’d better go before it starts.
• You’d better not touch that cake! It’s for your grandparents’ anniversary.

Conclusion

Ready? Terrific! Let’s move on to step 4 to practise what you’ve learnt in this step.