Adpositions include prepositions and postpositions. They are used to express spatial and temporal relations. Languages such as English have prepositions, words which are placed before nouns. In other languages such as Finnish, Hungarian, Korean and Japanese, however, postpositions, words placed after nouns, are used. As a result, adpositions refer to both types.
English uses prepositions to create phrases such as in Vancouver and in Toronto. In Hungarian, though, the phrase in Vancouver is expressed with Vancouverben. The suffix -ben is a postposition. The phrase in Toronto is expressed in Finnish with Torontossa. The suffix -ssa is the Finnish postposition which corresponds to the English preposition in.
The word ago is usually analyzed as an adverb, but can also be considered a postposition. The reason is that it follows rather than proceeds the complement as in ten weeks ago. In addition to prepositions and postpositions, languages also use circumpositions. These consist of two parts and are placed before and after the complement. The Norwegian phrase for tre uker siden (three weeks ago) is an example of a circumposition with one word before tre uker (three weeks) and another after.
Adpositions are words which indicate spatial and temporal relations. These are usually expressed with prepositions, but they also include postpositions and circumpositions. Prepositions are more common than postpositions.