You don’t have to help.
Would somebody please weigh in on the difference between using “brauchen” and “müssen” to mean “need to do (something)”? I only just across “brauchen” in this sense of “need to do” rather than “have need (of something)”.
“Ihr braucht nicht zu helfen.”
“Ihr müsst nicht helfen.”
These two sentences are interchangeable.
Personally, I perceive the first one as more colloquial.
Note the difference of usage (Infinitiv mit zu vs. Infinitiv)
“Ihr braucht nicht helfen.” is only acceptable in informal speech.
Same in English with “you need to” versus “you have to”. They’re more or less interchangeable. Things get a little interesting when you want to invert the sentence, though: “you need not” is not at all the same (in English) as saying “you must not”, even though “du musst es nicht tun” and “du brauchst es nicht tun” are interchangeable in German. I did an episode on that subject just a few months ago.
One thing I want to add is that “brauchen” in this sense together with a verb can only be used in the negative. In positive sentences “brauchen” only works with things. So while “You need to help” may work in english, “Du brauchst zu helfen” does not work in german. For that, you’d have to resort to “musst”, or other forms such as “solltest”, “du hast zu”, or even “bist verpflichtet zu”, etc.
I think that’s because the necessity that “brauchen” expresses is not quite the same as obligation.
That being said, sentences like “Du brauchst nur zu helfen” do work, because then the meaning changes to “All you need to do is help”, or even “All it takes you is to help”.
Also beware that a sentence like “I need you to <do xyz>” cannot be translated literally to “Ich brauche dich zu <xyz tun>”, at least not when what you mean is “I want you to <do xyz>”. You would have to say something like “Ich möchte, dass du <xyz tust>”
Another “that being said”: “Ich brauche dich um xyz zu tun.” is okay because that essentially means “I need your help with <doing xyz>”, i.e. “I can’t do this alone”.