nine vs ix

nine is a noun but ix is not a noun.

Word	Noun	Adjective	Verb	Adverb
nine	Yes	Yes	No	No
ix	No	Yes	No	No

As adjectives, nine and ix are synonyms defined as:

nine and ix: denoting a quantity consisting of one more than eight and one less than ten

Other synonyms of nine include 9.

nine (noun)	ix (noun)
one of four playing cards in a deck with nine pips on the face
a team of professional baseball players who play and travel together
the cardinal number that is the sum of eight and one

nine (adjective)	ix (adjective)
denoting a quantity consisting of one more than eight and one less than ten	denoting a quantity consisting of one more than eight and one less than ten