A noun is a word that names a person, a place, a thing, or an idea. A singular noun names only one person, place, thing, or idea.
Here are some examples of singular nouns:
duck, dog, book, tree, house, train, car, mouse, school, clock, cookie, window, newspaper
Each of these nouns names only one thing:
one duck, one dog, one book, one tree, one house, one train, one car, one mouse, one school
A noun in simple form is a singular noun. Each singular noun names only one person, one place, one thing.
▶Find the three singular nouns in this sentence: Bob left his book in the car after school. Did you find them? Good for you!