* Noun: A word that names a person, place, thing, or idea. Examples: *dog, city, happiness, John*.
* Pronoun: A word that replaces a noun. Examples: *he, she, it, they, we*.
* Noun phrase: A group of words that functions as a noun. Examples: *the big red ball, my best friend, that beautiful sunset*.
* Clause: A group of words that contains a subject and a verb. Examples: *because she was tired, after the rain stopped, while I was waiting*.
Examples of subjects that are not nouns:
* Pronoun: *He* went to the store.
* Noun phrase: *The woman with the red hat* is my neighbor.
* Clause: *What she said* surprised everyone.
The important thing to remember is that the subject of a sentence is the part that performs the action or is described by the verb. It's the "who" or "what" of the sentence.