noun vs common noun

noun and common noun both are nouns.

Word	Noun	Adjective	Verb	Adverb
noun	Yes	No	No	No
common noun	Yes	No	No	No

As nouns, common noun is a hyponym of noun; that is, common noun is a word with a more specific, narrower meaning than noun:

noun: a content word that can be used to refer to a person, place, thing, quality, or action
common noun: a noun that denotes any or all members of a class

noun (noun)	common noun (noun)
a content word that can be used to refer to a person, place, thing, quality, or action	a noun that denotes any or all members of a class
the word class that can serve as the subject or object of a verb, the object of a preposition, or in apposition