Definition of: preposition

(prep′ə·zish′ən) noun Gram.
1. In some languages, a word functioning to indicate the relation of a substantive (the object of the preposition) to another substantive, a verb, or an adjective: one of the eight traditional parts of speech. Some English prepositions are by, for, from, in, to, with. A preposition is usually placed before its object (whence its name), and together they constitute a prepositional phrase which serves as an adjectival or an adverbial modifier: He sat beside the fire; sick at heart; a man of honor. There is a close relationship between certain prepositions and adverbs, and the same word may have either function, depending on the context: We saw it through (adverb); It sailed out through the window (preposition).
2. Any word or construction that functions in a similar manner: He telephoned in reference to (equals about) your letter.
—inseparable preposition A preposition so closely connected with a verb as to have all the force of a compound: to laugh at.
—participal preposition A participle used without direct connection with a subject, so that it has the force of a preposition: They spoke to him concerning that affair.
—postpositive preposition A preposition in postposition; also, a suffix added to a noun and serving as a preposition: Hope soars heaven ward. [<L praepositio, -onis <praepositus, pp. of praeponere place before <prae- before + ponere place]