Must and have to both express obligation.
However, they are used differently depending on who imposes the obligation. |
| MUST | HAVE TO |
| The speaker thinks it is necessary. | Someone else thinks it is necessary. |
|
|
- I must buy flowers for my mother.
(It's her birthday and I decide to do that.)
|
- I have to buy flowers for my mother-in-law.
(It is not my decision - my husband asked me to do it.)
|
- "You must take more exercise" says the doctor.
(The doctor thinks it is necessary.)
|
- I have to take more exercise.
(The doctor says it is necessary.)
|
- I must ask my secretary to book a flight for me.
(It is important for me not to forget.)
|
- I have to call the travel agency.
(My boss asked me to book a flight.)
|
- "Dogs must be kept on a lead."
(Written on a sign in the park = a rule which
must be obeyed.)
|
- I have to keep my dog on a lead.
(That's what the sign tells me to do.)
|
| |
| N.B. In the negative form, the meaning changes. |
- You mustn't tell George =
it is important not to tell George =
don't tell George.
|
- You don't have to tell George =
you can tell George if you like,
but it isn't necessary. It's your decision.
|
