* Noun: When it refers to the measurement of something from side to side.
* Example: "The width of the room is 10 feet."
* Adjective: When it describes something as being wide.
* Example: "The river was of width that could not be crossed."
* Adverb: This is less common, but possible. It would mean "widely" or "in a wide manner."
* Example: "The bird spread its wings width."
The most common usage is as a noun.