Must is the same as Have to, but still - not only are they different, but there's so much more to must than a naked eye could see.
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| photo credit Nina Paley |
to have to do something because it is necessary or important, or because of a law or order [past form: had to]:
- All passengers must wear seat belts.
- It's getting late. I really must go.
- You must work hard.
- We must all be patient.
used in negative sentences to say that something should not happen, because of a rule or law or because of the situation:
- You mustn't talk to your mother like that.
- This book must not be removed from the library.
- We must never forget how much we owe to these brave men.
- No one must disturb him while he's sleeping.
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| photo credit Nina Paley |
used to say you think something is very likely to be true or very likely to have happened:
- Sam must be nearly 90 years old now.
- His new car must have cost around £20,000.
- You must have been really upset.
- There must be something wrong with the engine.
- Karl must've seen 'Star Wars' six or seven times.
especially British English (spoken), used to suggest that someone should do something, especially because you think they will enjoy it or you think it is a good idea:
- You must come and stay with us in London sometime.
- 'We must do this again,' he said. 'I've enjoyed it thoroughly.'
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| photo credit Nina Paley |
especially British English (spoken), used to say that you intend or want to do something:
- I must call her tonight.
- I must do this later.
I must admit/say/confess (spoken), used to emphasize what you are saying:
- I must say, it gave me quite a shock.
why) must you...? (spoken), used to tell someone that their behaviour upsets or annoys you:
- Must you spoil everything?
- Why must you always be so suspicious?
a must-have/must-see/must-read etc /informal, something that is so good, exciting, or interesting that you think people should have it, see it etc:
- The exhibit is a must-see for anyone interested in Japanese art.
- Now, that's a must-read novel
if you must (do something), spoken, used to tell someone that they are allowed to do something, but that you do not approve of it or agree with it:
- All right, come along, if you must.
- If you must smoke, please go outside.
if you must know, spoken, used when you answer a question that you think someone should not have asked, because it is slightly impolite:
- Well, if you must know, I'm thirty-six.
[source: Longman Contemporary Dictionary]
