Studying the German language, learners come across modal verbs which can express desire, ability, obligations or probability. In German, we conjugate the modal verb which then retains second position in a main clause. The main verb is added in its infinitive form to the end of the sentence.
For example: Ich darf meine Hausaufgaben nicht vergessen.
Now what is the main challenge English speakers face when using these verbs in German? To express something that is not permitted, English speakers use ‘must’ plus a negator. Surely, you’ve heard your German tutor say: You must not forget your homework. The clanger many English speakers fall for in German is to translate this verbatim by using ‘müssen’ with a negator plus the main verb. In German however, ‘nicht müssen’ leaves another option and translates as ‘doesn’t have to’. To express something that is forbidden (verboten), German uses the modal verb ‘dürfen’ plus a negator: nicht dürfen = verboten. Remember, you must not forget your homework.
Sie dürfen Ihre Hausaufgaben nicht vergessen.