WordWeb Online

1. A function word that combines with a noun or pronoun or noun phrase to form a prepositional phrase that can have an adverbial or adjectival relation to some other word
    
2. (linguistics) the placing of one linguistic element before another (as placing a modifier before the word it modifies in a sentence or placing an affix before the base to which it is attached)

Derived forms: prepositions

Type of: closed-class word, function word, place, position

Encyclopedia: Preposition