The person who does the action in a sentence is the subject of the sentence. A proper noun often acts as the subject of a sentence.
In these sentences, a proper noun is the subject of the sentence:
Mary threw the ball to the catcher.
Janet walked through the park.
Sam did his math homework.
Mr. Davies teaches math at our school.
Each dark word is a proper noun working as the subject of the sentence.
Sometimes a common noun is the subject of the sentence. Look at these examples:
The rain just won’t stop!
The train is late tonight.
My dog found a bone.
Each dark word is a common noun. That common noun at the beginning of the sentence is doing something.
The noun that does the action in a sentence is the subject of the sentence.
Even an abstract noun can work as the subject of the sentence if the abstract noun is doing the action.
Horror fills every corner of the haunted house.
Success almost always follows hard work.
Equality promises a fair chance for everyone.
A noun works as the subject of a sentence. Proper nouns, common nouns, and abstract nouns all work as the subject of a sentence. A subject does the action in a sentence.