A singular noun names one person, one place, or one thing.
A plural noun names more than one person, place, or thing.
You can add a s to most nouns to make it plural.
I like to read with my friend.
I like to read with my friends.
There is a light blue house.
There are two blue houses in a row.
An apple a day keeps the doctor away.
Apples are good for us.