must, have to

To tell you the truth, you are not alone. Most native english speakers don't get it either, and just use "have to" instead of "must" in almost every instance.

In your first sentence, using the word "must", it is implied that the person saying it is the one putting the requirement/obligation on the other person. It's that person's stipulation, in other words. Mother is saying that SHE doesn't approve of you wearing those dreadful jeans.

In the second one, using "have to", it could actually mean the same thing, but in most cases, the implication with this usage is that there is this obligation placed on the situation by someone other than the speaker. For instance, mother might have just spoken with the owner of the opera house and found that they will not let anyone in that is wearing jeans.

Wow, that is a hard one to explain...I hope I have helped at least a little bit. I'm sure there are others that can and will explain it better than I just did.

Hi kickycan, and thanks. Got that but still confused. It's me. I'd tell what I know,

Must expresses obligation imposed by the speaker,

Mother: You must wipe your feet when you come in.

Have to expresses external obligation,

Small boy: I have to wipe my feet every time I come in.

I take it ( not sure though ) that must indicates the speaker has an authority over the listener ( mother here ) .

It is not required that the speaker has actual authority over the listener (as in the power to enforce laws, exact obedience, or command), but that the speaker perceives himself or herself as having the power to influence or persuade as a result of knowledge or experience.

"You must wear those shoes with that handbag," is not likely to require obedience from the speaker but, rather, intend to convey expertise.

I don't think either 'must' or 'have to' implies which direction the obligation comes from - that's specified in the context. In your context, the mother clearly doesn't want her daughter to wear jeans to the opera, but she's being nicer than simply saying "I'm going to force you to wear a dress" or something to that effect. You can actually use "must" in contexts where it's hard to see any 'obligation' at all - "it must have been one of those days" which can still be used with "have to" - "it had to have been one of those days". I think they're pretty synonymous. "Need to" is slightly synonymous, but it has even more of an impersonal connotation. It's not uncommon for someone to use the other two to imply an order, but if you use "need to" for the same purpose, it's very euphemistic.

Hi everybody, and thanks.

I'm having a difficult time finding a definitive explanation of the differences, but I would agree with you, Rufio, that the context could change the "direction" of the obligation without sounding incorrect. (Then again, repeated corruption can eventually make anything sound correct.) On another forum, I found another explanation:

We use have to if we want to express an objective obligation, that means something is obligatory, for example:

My father has to work 8 hours every day.
You have to study at university if you want to obtain my MBA.

We use must to express a subjective obligation. A subjective obligation is something essential or nessary, for example:

I must leave now. or You must come to our party. (you simply can't afford missing it)

What do you think?

Hi All,

A friend told me that in order to know exactly when to use Must or when to use Have.

Just put the sentences in negative form, then think about the sense of it.

Hope this will help.