Preposition and postposition
Prepositions are a grammatically distinct class of words whose most central members characteristically express spatial or temporal relations or serve to mark various syntactic functions and semantic roles. In that the primary function is relational, a preposition typically combines with another constituent to form a prepositional phrase, relating the complement to the context in which the phrase occurs. The word
preposition comes from Latin, a language in which such a word is usually placed before its complement, thus it is "pre-positioned". English is another such language, though there is no requirement that the preposition precede a complement. In many languages, the words with this grammatical function come after, not before, the complement. Such words are then commonly called
postpositions. Similarly,
circumpositions consist of two parts that appear on each side of the complement. The technical term used to refer collectively to prepositions, postpositions, and circumpositions is
adposition. Some linguists use the word "preposition" instead of "adposition" for all three cases.