content word vs open-class word

content word and open-class word both are nouns.

Word	Noun	Adjective	Verb	Adverb
content word	Yes	No	No	No
open-class word	Yes	No	No	No

As nouns, content word and open-class word are synonyms defined as:

content word and open-class word: a word to which an independent meaning can be assigned

content word (noun)	open-class word (noun)
a word to which an independent meaning can be assigned	a word to which an independent meaning can be assigned