The of a sentence is the noun that is carrying out the main action or the noun that is being affected by the main verb.

The term you are looking for is "subject" for the noun that is performing the action, and "object" for the noun that is being affected by the action of the main verb in a sentence.

In grammatical terms:

1. Subject: The subject of a sentence is typically the noun or pronoun that performs the action of the verb. For example, in the sentence "The dog barks," "the dog" is the subject because it is the one performing the action of barking.

2. Object: The object is the noun or pronoun that receives the action of the verb. In the sentence "The cat chased the mouse," "the cat" is the subject (performing the action) and "the mouse" is the object (receiving the action).

Understanding these roles helps in analyzing sentence structures and enhances both writing and grammar skills.