Must and Have To

Must and have to both express obligation. However, they are used differently depending on who imposes the obligation.

MUST

The speaker thinks it is necessary.

-I must buy flowers for my mother(It's her birthday and I decide to do that)

-"You must take more exercise"says the doctor. (The doctor thinks it is necessary).

-I must ask my secretary to book a flight for me. (It is important for me not to forget.)

-"Dogs must be kept on a lead"(Written on a sign in the park = a rule which must be respected)



HAVE TO

Someone else thinks it is necessary.


-I have to buy flowers for my mother-in-law. (It is not my decision - my husband asked me to do it.)

-I have to take more exercise.(doctor's orders!)

-I have to call the travel agency. (My boss asked me to book a flight.)

-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!


MUST NOT (MUSTN'T)
You mustn't tell George = it's important not to tell George = don't tell George

DO NOT HAVE TO (DON'T HAVE TO)
You don't have to tell George = you can tell George if you like, but it isn't necessary. It's your decision.

from: LEarn English Today