I was watching a TV program about penguins last night. There were some scientists in the South Pole studying them. While I think they must have an interesting job, I can’t imagine how they can work there. It must be so cold. It can’t be a comfortable place to work. I’m sure it must have been at least twenty degrees below zero! Still, it must be interesting to work in such a beautiful, natural environment. Of course, when they go outside they must dress warmly. And since they can go for months without having the opportunity to leave, they must prepare for living in isolation.
The word must has a few different uses in English. Do you know how to use them? Take a look at the paragraph above and then check out today’s lesson:
We can use must when make conclusions that something is certain:
- It must be so cold = I’m sure it is so cold there, based on what I have seen.
- They must have an interesting Job = I concluded their job is interesting after watching that program.
- That child is crying. He must have hurt himself.
When we make conclusions that something is not certain, we use can’t and not mustn’t.
- It can’t be a comfortable place to work. Not, It mustn’t be a comfortable place to work.
- She can’t be happy living so far from home. Not, She mustn’t be happy…
When we talk about conclusions of certainty in the past, we can use must+have+PP, like this:
- It must have been at least twenty degrees below zero.
- You must have enjoyed your trip to Egypt.
- They must have gone out. Nobody has answered the door.
Must is also used when we talk about something that is obligatory or a necessity, like this:
- You must water your flower garden, or the plants will die.
- I must stop drinking coffee.
- We must reach the station by 3:00, or we’ll miss the train.
In American English, we prefer to use have to when we talk about something that is obligatory or a necessity in conversation, and in questions about something that is obligatory or a necessity:
- Do you have to wear a suit and tie to work?
- I have to stop drinking so much coffee.
Well, I have to finish this lesson now because I must go eat dinner. You must study all of my lessons 🙂 ! What do you have to do today?