A preposition is a word which shows relationships among other words in the sentence. The relationships include direction, place, time, cause, manner and amount. In the sentence She went to the store, to is a preposition which shows direction. In the sentence He came by bus, by is a preposition which shows manner. In the sentence They will be here at three o’clock, at is a prepositionwhich shows time and in the sentence It is under the table, under is a preposition which shows place.
A preposition always goes with a noun or pronoun which is called the object of the preposition. The preposition is almost always before the noun or pronoun and that is why it is called apreposition. The preposition and the object of the preposition together are called a prepositional phrase. The following chart shows the prepositions, objects of the preposition, and prepositional phrases of the sentences above.