Proper nouns vs. common nouns

One important distinction to be made is whether a noun is a proper noun or a common noun. A proper noun is a specific name of a person, place, or thing and is always capitalized.

Does Tina have much homework to do this evening?

Tina is the name of a specific person.

I would like to visit Old Faithful.

Old Faithful is the specific name of a geological phenomenon.

The opposite of a proper noun is a common noun, sometimes known as a generic noun. A common noun is the generic name of an item in a class or group and is not capitalized unless appearing at the beginning of a sentence or in a title.

The girl crossed the river.

Girl is a common noun; we do not learn the identity of the girl by reading this sentence, though we know the action she takes. River is also a common noun in this sentence.