Here's a breakdown:
* Subject: The part of a sentence that tells us who or what is doing the action.
* Complete Subject: The subject noun along with any words that modify it.
* Subject Noun: The core of the subject, the word that names the person, place, thing, or idea performing the action.
Example:
* The big red ball bounced across the room.
In this example:
* Complete Subject: The big red ball
* Subject Noun: ball
The subject noun "ball" is the core of the subject, and the words "big" and "red" modify it.