Prepositions

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Definition

• A preposition is a word or set of words that indicates location (in, near, beside, on top of) or some other relationship between a noun or pronoun and other parts of the sentence (about, after, besides, instead of, in accordance with). A preposition isn't a preposition unless it goes with a related noun or pronoun, called the object of the preposition.

Examples:
Let's meet before noon.
Before is a preposition; noon is its object.

We've never met before.
There is no object; before is an adverb modifying met.