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.
- He went to the races.
- He promised to help with whatever was the matter.