Must instead of have to

[Rachel Adams]

Hello.

Is it wrong to say that 'must' and 'have' are not quite interchangeable? Do both of them work in my sentences? If it is a strict obligation I should use 'must' if it's not as strict as with 'must' I can use 'have to'. Am I right?

1. 'You must call the instructor if you want to change the time of your sessions.'

2. 'You have to call the instructor if you want to change the time of your sessions.'

3. 'You must wear appropriate footwear in the gym.'

4. 'You have to wear appropriate footwear in the gym.'

5. 'I would like to apply for this job.' 'Well, you must fill in this form.'

6. 'I would like to apply for this job.' 'Well, you have to fill in this form.'

7. 'I have an injury. 'Well, you really must tell the instrucor about it.'

8. 'I have an injury.' 'Well, you should really tell the instructor about it.'

 

[probus]

To me there is no actual difference in meaning between "must" and "have to". It is merely a small difference in tone or register, "must" being slightly more formal and "have to" a little more casual. But the difference is so tiny that other native speakers may disagree. (Cross posted with Piscean.)

 

[probus]

We agree on that

Well that worked out nicely Rachel Adams. You have the BrE view from Piscean and the AmE view from me. It reminds me of The Two Ronnies who would end their show with:

Ronnie1: "It's goodnight from me."
Ronnie2: "And it's goodnight from him."

 

[Rachel Adams]

No. They are often not interchangeable There is also the point that some speakers, particularly in North America, rarely, if ever, use 'must.
They can do, but they may have slightly different meanings. I see that in #8, you have used neither 'must' nor 'have to'

No.
In #1-#7, 'must' suggests to me an an obligation imposed by the speaker, 'have to' an externally imposed obligation. Other native speakers may feel differently.

I understand what you are talking about. For an obligation that comes from outside you use 'have to' and and when it comes from the speaker you use 'must'. Here they are not interchangeable. The first difference.
When giving strong advice to myself and other people you use 'must' but are they used interchangeably? 'I must call my sister.' 'You must come on time.'
Yes, sorry. I was going to write 'have to'/'must' in the eighth sentence. This is the situation I am asking about. If the assistant uses 'have to' in the eighth sentence instead of 'must' would he/she sound less strict? Are they inerchangeable?
Or are they used interchangeably when we are talking about the law. 'Children have to start school when they are five.'
And instructions/orders 'Visitors must contact us upon arrival'. Sorry, lots of questions but modals are really confusing.

 

[Yankee]

Hello.

Is it wrong to say that 'must' and 'have' are not quite interchangeable? "Wrong" ? No, depends on context and word stress. Do both of them work in my sentences? Yes. But in 7. and 8. with "really" and "should" in 8., it's a strong recommendation. If it is a strict obligation I should use 'must' if it's not as strict as with 'must' I can use 'have to'. Am I right? OK as a general rule, but context and word stress are also important in choice.
1. 'You must call the instructor if you want to change the time of your sessions.'

2. 'You have to call the instructor if you want to change the time of your sessions.'

3. 'You must wear appropriate footwear in the gym.'

4. 'You have to wear appropriate footwear in the gym.'

5. 'I would like to apply for this job.' 'Well, you must fill in this form.'

6. 'I would like to apply for this job.' 'Well, you have to fill in this form.'

7. 'I have an injury. 'Well, you really must tell the instrucor about it.'

8. 'I have an injury.' 'Well, you should really tell the instructor about it.'

Y