I've been taught that the word "shall" represent obligatory or mandatory. On the other hand, I was taught by another lecturer that "must" represent mandatory.

Which one of the two represents obligatory. When I asked a teacher this question, he told me "shall" is also synonymous to might or maybe. Is this true?

As an example, consider;

He shall report the case to his senior officer.

He must report the case to his senior officer.

  • 1
    The meaning of shall to a large extent depends on tone (as well as context). In the first example, if it is expressed with emphasis on shall, it is more or less a command; if there is no emphasis on shall, then it is more of a predictor (or at any rate, less commanding). There are also differences in uses between NAE and BrE (the use of shall is more common in the latter). – David Handelman Nov 17 '16 at 15:49
  • Must is closer to being uniformly obligatory. – David Handelman Nov 17 '16 at 15:49
  • I've noticed that some people whose first language is not English use shall when then really mean should. Dunno why, or how this habit developed. A guess is that their first language might be German (?). – Drew Nov 17 '16 at 18:42

"Shall" is not synonymous with "might" or "maybe." It is synonymous with "will."

"Must" carries the semantics of mandatory action more than "shall."

In Australian and UK varieties of English (I can't speak for American) "shall" is on the way out, being replaced by "will." I think originally the semantic difference between the two words was that "shall" simply indicated that the action would take place in the future, and "will" had more of a personal intention element, but that distinction has disappeared.


Nobody uses "shall" in common speech. It's one more example of unnecessary lawyer talk. Nobody says, "You shall finish the project in a week."

For all these reasons, "must" is a better choice

In general, must is used if the sentence’s subject is an inanimate object, in other words, where the subject is not a person or a body on which a duty can be imposed.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for?Browse other questions tagged or ask your own question.