content word vs noun

content word and noun both are nouns.

Word	Noun	Adjective	Verb	Adverb
content word	Yes	No	No	No
noun	Yes	No	No	No

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

content word: a word to which an independent meaning can be assigned
noun: a content word that can be used to refer to a person, place, thing, quality, or action

Other hyponyms of content word include head word, headword, verb, modifier, qualifier, numeral.

content word (noun)	noun (noun)
a word to which an independent meaning can be assigned	a content word that can be used to refer to a person, place, thing, quality, or action
	the word class that can serve as the subject or object of a verb, the object of a preposition, or in apposition