In grammar, an ad-position is an element that combines syntactically with a phrase and indicates how that phrase should be interpreted in the surrounding context. "Ad-position" is a general term that includes the more specific labels preposition, post-position, and circumposition, which indicate the position of the ad-position with respect to its complement phrase. In linguistics, all of these are considered to be members of the syntactic category "P". Ad-positional phrases (or "PPs", consisting of an ad-positional head and its complement phrase) are used for a wide range of syntactic and semantic functions., most commonly modification and complementing. The following examples illustrate some uses of English prepositions:
modifiers
(of verbs) sleep through the winter, danced on the tables for hours.
(of nouns) the weather in April, cheeses from France with live bacteria
complements
(of verbs) insist on staying home, dispose of unwanted items
(of nouns) a thirst for revenge, a message to our customers
(of adjectives/adverbs) attentive to their needs, separately from its neighbours
(of other ad-positions) away from the window, from under the bed
Ad-positions perform many of the same functions as case markings, but ad-positions are syntactic elements, while case markings are morphological elements.