all about preposition A preposition is a word or group of words used before a noun, pronoun, or noun phrase to show direction, time, place, location, or spatial relationships, or to introduce an object. Some examples of prepositions are words like "in," "at," "on," "of," and "to." Prepositions in English are highly idiomatic. There are five types of prepositions. They are simple, double, compound, participle, and phrase prepositions. A preposition is used to show a relationship between the noun, pronoun, or phrase in a sentence.