Relations of place, time, and abstract connection need compact markers. A preposition is a word that typically stands before a noun phrase and links it to the rest of the clause, expressing relationships such as location, direction, time, or cause.

English prepositions include in, on, at, by, and many others. Some languages use postpositions instead, following the noun phrase. Prepositional phrases function as modifiers or complements within larger structures.

Idiomatic preposition choice is a major challenge for language learners. Descriptive grammars list prepositions and the types of complements they take. Grammaticalization studies show how many prepositions developed historically from verbs or nouns.

• Word linking a noun phrase to the clause
• Expresses spatial, temporal, and abstract relations
• Heads prepositional phrases
• Often idiomatic and hard for learners