Excellent definition of Common noun

Common noun
: a word (such as “singer,” “ocean,” or “car”) that refers to a person, place, or thing but that is not the name of a particular person, place, or thing.
Also a noun that may occur with limiting modifiers (as a or an, some, every, and my) and that designates any one of a class of beings or things. Yet it refers to an object or thing.
It's a name given to a group of similar things or persons.
Examples in sentence
I bought a car.
She is a singer.
Neither the girls nor boys is here.
I went the shop.
She's learning to derive a car.
Are you going on the car.
Where can I park my car.
How did you come ?by car.
He was a shy boy, but he grew to be a strong and confident man.
He's a grown man now.
The movie is popular with men and women.
References:
Oxford dictionary
Merriam Webster dictionary
Y. A. Salees