A proper noun is the name of some particular person,
place, or thing. Proper nouns are always capitalized.
For example: Abraham Lincoln,
Canada, Central Park, Statue of Liberty
A common noun is the name given in general to every
person or thing of the same class or kind.
For example: girl, blue whale,
city, clock
Common nouns are not capitalized unless they are the first
word of the sentence. For example, look at the two sentences below.
Girls won the soccer match
between the boys and girls in our class.
The girls in Hannah's bus make
too much noise.
In the first sentence, the common noun “girls” is the first
word of the sentence, so it is capitalized. In the second sentence, “girls” is
not the first word of the sentence, so it is not capitalized.