Ich habe vergessen, das Fenster zu schließen.
English: I forgot to close the window.
The 'Infinitiv mit zu' in German is a structure where you use 'zu' with the infinitive form of a verb. It is similar to saying 'to do' something in English.
You use 'Infinitiv mit zu' in German after certain verbs, adjectives, and nouns. It is often used when you want to express purpose, intentions, or after expressions like 'es ist wichtig', 'ich habe Lust', or 'ich hoffe'.
Ich habe vergessen, das Fenster zu schließen.
English: I forgot to close the window.
Es ist wichtig, pünktlich zu sein.
English: It is important to be on time.
Ich habe keine Zeit, dir zu helfen.
English: I have no time to help you.
Sie hofft, bald Urlaub zu machen.
English: She hopes to go on vacation soon.