In grammar, a preposition is a part of speech that introduces a prepositional phrase. For example, in the sentence "The cat sleeps on the sofa", the word "on" is a preposition, introducing the prepositional phrase "on the sofa". In English, the most used prepositions are "of", "to", "in", "for", and "on". Simply put, a preposition indicates a relation between things mentioned in a sentence.
Linguists sometimes distinguish between a preposition, which precedes its phrase, a postposition, which follows its phrase, and as a rare case a circumposition, which surrounds its phrase. Taken together, these three parts of speech are called adpositions. In more technical language, an adposition is an element that, prototypically, combines syntactically with a phrase and indicates how that phrase should be interpreted in the surrounding context. Some linguists use the word "preposition" instead of "adposition" for all three cases.
In linguistics, adpositions are considered to be members of the syntactic category "P". "PPs", consisting of an adpositional head and its complement phrase, are used for a wide range of syntactic and semantic functions, most commonly modification and complementation. The following examples illustrate some uses of English prepositional phrases:
