An "infinitive" in English is a verb preceded by the word to, as in to study. Many English verbs can be followed by a grammatical structure that contains an infinitive and is known as an "infinitive ...

In addition, some of these verbs need an object, usually a person or people. The police warned us not to enter the building. The speaker invited the audience to ask questions. The best way to learn ...

In an um...zu... clause, the infinitive has to be at the end. But when using a separable verb, you 'separate' the prefix and the rest of the infinitive by inserting ...