the difference between "must" and "have to"

hshmy2020 · #1 27-03-2010, 01:31 PM

the difference between "must" and "have to"

hshmy2020 · #2 27-03-2010, 01:34 PM

There have been a lot of questions from Secondary 2 teachers about the modal verb must and the semi-modals have to and need to. Sometimes these can be used interchangeably and sometimes there is a difference. If you are writing exercises and exams, keep these points in mind:

In MCQs, write items so that only one choice is grammatically correct, OR
Give students enough context so they can choose the correct answer.
In other types of questions, when more than one answer is possible, allow for that in your answer key.

See the questions and answers in the grammar section of this website for examples of the above.

We are talking here about must used to show obligation or necessity or to give orders or strong advice. We are not talking here about must used to show certainty in a logical conclusion.

In Preparatory 3 and Secondary 1 grammar, must and have to were treated as equal in meaning in the affirmative. The emphasis in those years was on the difference in meaning in the negative. In Secondary 2 grammar, the emphasis is on the differences between must and have to and need to. But if you look back at the textbooks and tapescripts from Prep 3 and Sec 1, you will see that the rule is followed, though it is not stated.

Also note that these differences mainly apply to British English. If you read or hear American English, you will find that must is less often used, and this distinction is rarely found.

Again, in meaning must and have to are largely interchangeable. But there is sometimes a difference in where the obligation comes from.

In the first person (subject is I or we) have to often refers to an external authority -- a regulation or order -- or circumstances that make something obligatory. In other words, as the Sec 2 SB states (page 102), when we cannot choose whether or not to do something.

My children have to study ancient history at school next year. (a school requirement)

My staff and I have to work twelve hours a day. (circumstances)

We have to be back in Cairo on Friday in time for our flight. (circumstances; our scheduled flight)

In the first person, must is often used to express the speaker’s authority over himself. It is the speaker’s strong feelings or wishes that make him that make him feel something is obligatory. In other words, as the Sec 2 SB states (page 102), to express strong feelings or wishes.

We must buy souvenirs for our friends. (my opinion or feelings)

We mustn’t forget that tourism is very important for Egypt. (my opinion)

Must is also used to give strong advice and orders to ourselves or others, and to give emphatic invitations.

You must clean your room before you go out with your friends.

You must come visit us sometime soon.

In the negative, mustn’t and don’t have to are not interchangeable. Mustn’t means that something is forbidden. Don’t have to means that it is not necessary.

Have to and need to are often interchangeable to say that something is necessary. However, need to is more often used in the negative.