What is an adposition?

Definition
	An adposition is a cover term for prepositions and postpositions. It is a member of a closed set of items that
	occur before or after a complement composed of a noun phrase, noun, pronoun, or clause that functions as a noun phrase, and form a single structure with the complement to express its grammatical and semantic relation to another unit within a clause.

Examples (English)
	He went to the races. He promised to help with whatever was the matter.

Kinds
	Here are some kinds of adpositions:
	What is a postposition? What is a preposition?

Generic
	An adposition is a kind of
	What is a word? What is a relator?