* Preposition: This is the most common usage. It indicates location, time, or subject matter.
* Example: "The book is about the history of computers."
* Adverb: In this case, it modifies a verb, adjective, or another adverb, usually indicating approximate quantity or degree.
* Example: "She's about to leave." (modifies the verb "leave")
* Example: "The room was about the size of a small car." (modifies the adjective "small")
* Interjection: This is less common, but it can be used to express surprise or uncertainty.
* Example: "About! Did you see that?"
To determine the specific grammatical function of "about" in a sentence, you need to look at the context and how it relates to the other words around it.