A noun is a word used to name a person, animal, place, thing, or an abstract idea. Nouns are usually the first words which small children learn. The bold words in the following sentences are all nouns:
"Jesus will return to set up His kingdom on Earth."
"Philosophy is of little comfort to the starving."
"Homosexuality is an abomination."
A proper noun is a noun that is capitalized. Not all, but most, capitalized words are also proper nouns. The most common exception is the word "I" which is a pronoun.
- The Writing Centre, University of Ottawa