"They told her over and over again that she must not do it." is a correct sentence. Is "should" OK instead of using "must" in this sentence? If so, "They told her over and over again that she not do it." might be OK, too?

  • No. What line of reasoning leads you to believe it might be?
    – Jim
    Jun 23 '14 at 4:49

They told her over and over again that she should not do it is OK.

They told her over and over again not to do it is also OK.

Those two sentences and your original sentence (with must not) are all correct, but they do not mean the same thing.

(They told her over and over again that she not do it is not grammatically correct, however.)

  • I'm not sure what you mean by your final sentence, but I certainly don't think it's normal to use the subjunctive with to tell in this way. It works with ask, demand, suggest, etc., so you can say "I suggest [that] you reconsider", but you really can't say "I told her [that] she reconsider". Jun 23 '14 at 14:25
  • @FumbleFingers: I don't understand your comment. You mention my final sentence (... is not what you want), but I don't see that what you say has anything to do with that sentence (or with anything else I wrote). What am I missing?
    – Drew
    Jun 23 '14 at 17:37
  • I mean I don't understand what you mean by "is not what you want". What I know is that "They told her over and over again that she not do it" is completely ungrammatical (although it would be valid with other verbs such as asked). It's not clear to me if that's the point you're making, or if you're simply saying that sentence doesn't carry the meaning OP wants to convey. Jun 23 '14 at 17:43
  • @FumbleFingers: OK, sorry; yes, that's what I meant: that sentence is ungrammatical. (I didn't say why, however, so your comment about to tell not taking the subjunctive is helpful.)
    – Drew
    Jun 23 '14 at 17:50
  • In light of which I assume your "Those 3 sentences are correct" is a typo (s/b 2). I could probably have figured that out if I'd looked at at your ELU profile - but I didn't, and there's not really enough of your own text in this answer to give me a clear indicator of whether you're a native speaker. Jun 23 '14 at 18:08

The words "must" and "should" are often interchangeable, but at the same time, there is a clear difference in meaning.

You must (or, more commonly, have to) do x means there is some external reason to do x: there is a rule, or a logical requirement.

  • To pass the course, you must complete the final project.
  • I have to buy some flour this afternoon, because I'm baking bread tonight.
  • You have to obey the safety regulations, or you'll be arrested.
  • We can have this conversation later, you have to go now, or you'll miss the talk.
  • You have to pay your taxes.

You should (or, sometimes, ought to) do x means that it is of a benefit to you, or, that it is the morally correct thing to do.

  • To do well in the course, you should study every night.
  • I should buy some flour this afternoon, in case anyone wants to bake bread later.
  • You should obey the safety regulations, or you might hurt yourself or someone else.
  • You ought to go, you look very tired!
  • You should give money to charity.

Less precisely, we can think of "should" as a "lighter" version of "have to," which is why both of them work in many sentences (with only a very subtle distinction in meaning). However, there are definitely sentences where we can contrast them.

You don't have to attend the lecture, but you should.

This suggests that there is no rule or other sort of obligation on the listener to go to the lecture, but that the listener will nonetheless benefit from going (or perhaps, that going is the morally correct thing to do).

Back to your sentence.

They told her over and over again that she (must not)/(should not) do it.

With "must," you suggest that there is a (formal or informal) policy in place, and that it would be a violation of the policy to do this thing. (Or at least that "they" think this.)

With "should," you suggest that it would be a strategic mistake (or ethically wrong) for her to do this thing. (Or at least that "they" think this.)

There are many contexts in which your sentence could appear where both words would be acceptable, and where the meaning would be only subtly different.

Your third sentence, with neither "must" nor "should," does not work at all after "told". You might be thinking of something else; namely, it works with some other verbs, "asked" or "demanded," but is a bit archaic sounding. (It is the subjunctive.)

  • Thanks for very much your comment. If I use "have to" instead of "must" in this sentence, it would be "They told her over and over again that she had not to do it." or just "has't to"?
    – user8229
    Jun 23 '14 at 10:59
  • actually, these words behave weirdly when they are negated (that is a whole separate question in and of itself). In that case, I would use "must," just the way you had it.
    – hunter
    Jun 23 '14 at 11:13
  • Thanks again! How about positive sentences using "have to" or "had to"? 1."They told her over and over again that she must do it." 2."They told her over and over again that she has to do it." 3."They told her over and over again that she had to do it."
    – user8229
    Jun 23 '14 at 12:17
  • 1
    (1), (2), and (3) are fine. (3) implies her obligation to do whatever it is was in the past, whereas (2) implies it is ongoing.
    – hunter
    Jun 23 '14 at 12:17
  • If you want to use "have", you could say, "They told her that she does not have to do it." But that doesn't mean quite the same thing. That means, she is not required to do it, which is not the same as, she is required to not do it. You could conceivably say, "She has to not do it," but that is considered awkward and confusing.
    – Jay
    Jun 23 '14 at 15:47

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