1. Subject: The noun that performs the action of the verb.
* Example: *The dog barked loudly.* (Dog is the subject performing the action of barking)
2. Object: The noun that receives the action of the verb.
* Example: *He threw the ball.* (Ball is the object receiving the action of throwing)
However, nouns can also be:
* Object of a preposition: The noun following a preposition. *He sat on the chair. (Chair is the object of the preposition "on")*
* Appositive: A noun that renames or clarifies another noun. *My friend, John, is coming over.* (John is an appositive renaming "friend")*
* Direct address: A noun used to directly address someone. *Mom, can I have a cookie?* (Mom is the noun in direct address)
* Complement: A noun that completes the meaning of a verb or adjective. *She is a teacher. (Teacher is the complement of the verb "is")*
So, while subject and object are the two most common roles, nouns can take on a variety of other roles in a sentence.