To me "I must help her" sounds wrong. I feel that I would rarely say this.

On one website they say that 'must' is more for personal obligations (e.g. I must help my mother.) and that 'have to' is for external obligations (e.g. my boss says I have to finish the report.)

Is it that simple (and vague)? Or does anyone have a better explanation?


they say that 'must' is more for personal obligations.

That is not true; when somebody says "you must show your ID card," it is referring to an external obligation (e.g. by a law) not to an obligation you personally have because your ideas.

|improve this answer|||||

Mmmm, that's a subtle distinction that I think the website is inventing or imagining. To my ear, "must" is simply more formal.

|improve this answer|||||
  • I concur, on both counts. – Brian M. Scott Sep 15 '11 at 8:19
  • @Malvolio that's how I feel as well. I just don't want to step into a classroom and say "in my opinion" and have no proof that I am correct! – Istable Sep 15 '11 at 8:23
  • 1
    In matters of connotation, I don't know what else you can do -- short of assembling a panel of experts -- other than say "in my opinion, as a native speaker, ..." Actually, I just got an official english.SE t-shirt in the mail today, so I guess you could try, "According to a guy wearing a convincing t-shirt..." – Malvolio Sep 15 '11 at 8:30
  • 2
    @Malvolio: I want a t-shirt that says "According to a guy wearing a convincing t-shirt ..." – Peter Shor Sep 15 '11 at 13:12
  • Agreed; I would hardly ever use "must" in ordinary conversation, unless referring to an attic. – JeffSahol Sep 15 '11 at 13:19

For me "I have to" can transport a unwillingness to do the task.

Sorry I can't come. I must help my Mum.

This is more formal and the speaker is more or less happy to help.

Sorry I can't come. I have to help my Mum.

More informal and can express that the speaker isn't happy with helping.

|improve this answer|||||

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.