Must & have to

Question

hello,I'm a bit confused with 'must' & 'have to' since I read that 'must' is used when we need to do sth, whereas 'have to' is the neccessity or sth that we are obliged to, when somebody else imposes sth on us. I saw a grammar exercise in which a student has to make a notice about a picture on which there is a sign 'no mobile phones allowed'. The answer in the key was ' you must turn off your mobile phone'.  Why ' must' if there is a kind of a obligation?  On the other hand , again in another  coursebook, there is a sentence like ' You must have your parents' permission to enter the club.' I will be grateful if someone gives me a clear explanation.

Markroe · Accepted Answer

I think you have a good understanding of the difference between these words. The reason for the confusion is that they basically mean the same. Must and have to can usually be used interchangeably. They are both used to express obligation or the need to do something. However, must generally expresses what the speaker thinks is necessary, while have to generally suggests that somebody else has imposed the decision.

I must stop smoking. (It's bad for me.)

I have to stop smoking. (The doctor told me so.)

CalifJim · Answer

jolantaadamskaI read that 'must' is used when we need to do sth, whereas 'have to' is the neccessity or sth that we are obliged to, when somebody else imposes sth on us.

This is very confusing. It doesn't make any sense to me. If I were you I would ignore it.

The remarks below apply to American English.

When must and have to are essentially synonymous in the 'obligation' meaning, the only difference I see is that must is used in more public and official contexts, such as on signs and in rules and laws, whereas have to is used everywhere else. Note that the first example was about a publicly posted sign, so must was the better answer. In the second example, must was better because the sentence was about the rules of a club.

Sign in a restroom: Employees must wash their hands before returning to work.
Published contest rules: You must be present at the drawing to win.
Traffic sign: Right lane must exit.
_____________

In addition to the must of obligation or requirement discussed above, there is also logical must, which is like prefixing a statement with "The only logical conclusion is that ...".

The dog is eating as if he hasn't had a meal in days. He must be hungry.
I can't believe what you're saying. You must be kidding.
Lisa is always laughing at Steve's stupid jokes. She must like him.
____________

If must and have to are used together, the must is logical must, not the must of obligation.

-- How do you get a new battery into this voice recorder?
-- I don't know. You must have to flip this thing open here.
(The only logical conclusion is that you are required to flip this thing open here.)

CJ

CalifJim · Answer

MarkroeI must stop smoking. (It's bad for me.)
I have to stop smoking. (The doctor told me so.)

This distinction may be true for British English. I don't notice anyone around me making this distinction in the U.S. I hear have to in both cases.

CJ

Markroe · Answer

CalifJim
MarkroeI must stop smoking. (It's bad for me.)I have to stop smoking. (The doctor told me so.)
This distinction may be true for British English. I don't notice anyone around me making this distinction in the U.S. I hear have to in both cases.CJ

Maybe that's because I'm Canadian. I realize that some of our English is more British than American. (I lived in Texas for more than a year.)

Khoff · Answer

CalifJimWhen must and have to are essentially synonymous in the 'obligation' meaning, the only difference I see is that must is used in more public and official contexts, such as on signs and in rules and laws, whereas have to is used everywhere else. Note that the first example was about a publicly posted sign, so must was the better answer. In the second example, must was better because the sentence was about the rules of a club.

I was going to say that in my mind, the only difference is that "must" is more formal and "have to" is more conversational. I think that agrees with what Jim is saying here.

Anonymous · Answer

hi must - you must turn off the mobile phone mean that you could not use it , becouse it is rule.

have to - you have to turn off the mobile phone mean that you can use it if you want, it is not necessary to turn off it .

I think it can help you.

Khoff · Answer

No, Anonymous.  If someone tells you that you have to turn off your mobile phone, it's not optional.

Abbos · Answer

I think sometimes there is a small distinction berween must and have to. If there had'nt been ever any diffrence between the meanings of them - whatever it might be, slight or big- there had been no need to use them in a diffrenet ways in speaking, writing etc... Because synonyms often ~~if not always~~ has a diffreent meanings from each other, that in case of right using or rather choosing one of them the sentence will be more eloquant or more suitable for the situation that is talked about.

Browsing internet I've found some interesting arguments about 'must' and 'have to'. And I'd like to share u one of them, which belongs to Mr. Micawber:

"Have to" and "must" have the same meaning in the affirmative and interrogative forms when referring to obligation. Some grammarians think that "must" is slightly stronger, but for all practical purposes, they mean the same thing:

Doctors have to attend medical school for several years before they can practice medicine.

Doctors must attend medical school for several years before they can practice medicine.

While "have to" and "must" can be used interchangeably, there are differences in usage, as Michael Swan observes in Practical English Usage (Oxford University Press, 1995):

Both verbs can be used in British English to talk about obligation. (In American English, 'have to' is the normal form.) British English often makes a distinction as follows. 'Must' is used mostly to talk about the feelings and wishes of the speaker and hearer — for example, to give or ask for orders. 'Have (got) to' is used mostly to talk about obligations that come from "outside" — for example from laws, regulations, agreements and other people's orders. Compare:

I must stop smoking. (I want to.)
I have to stop smoking. Doctor's orders.

This is a terrible party. We really must go home.
This is a lovely party, but we've got to go home because of the baby-sitter.

Must you wear dirty old jeans all the time? (Is it personally important for you?)
Do you have to wear a tie at work? (Is there a regulation?)
.

Chanchan · Answer

i agree with CJ

i just remember that 'must' is related to sth we need to do because of the rules, laws or obligation...

'must' also indicates the probability something can happen certainly (more than 95%); or logic things like CJ said.

'have to' is used for other cases

i might use 'had to' as the past-tense form of both 'must' and 'have to'.

CalifJim · Answer

abbosBritish English often makes a distinction as follows.
...
This is a terrible party. We really must go home.
...
Must you wear dirty old jeans all the time? (Is it personally important for you?)Just a brief comment. These two uses of must really do sound very British to my American ears -- actually, right or wrong, they sound very upper-class British.

CJ

Must & have to

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