A preposition is a word that combines with one or more noun or pronoun objects to form a prepositional phrase，which usually modifies some other words in a sentence．Commonly used prepositions include the following．

介词加上名词或代词宾语便构成介词短语，在句中起修饰作用。

beside　into　above　among　of　over

against　in　to　from　off　for

between　with　at　through　up　upon

along　by　after　besides　but　on