What is a preposition? A preposition is a word that tells you where something is or when something happens in a sentence. We usually use prepositions after the verb in a sentence. However, complex sentences can put prepositions before the noun and verb. There are special rules for how to put a preposition at the beginning of a sentence that we will not cover in this lesson. There are also other types of prepositions that students will learn about later in the program. Here is a video to help you