eightieth vs ordinal

eightieth and ordinal both are nouns.

Word	Noun	Adjective	Verb	Adverb
eightieth	Yes	Yes	No	No
ordinal	Yes	Yes	No	No

eightieth (noun)	ordinal (noun)
position 80 in a countable series of things	the number designating place in an ordered sequence

eightieth (adjective)	ordinal (adjective)
the ordinal number of eighty in counting order	being or denoting a numerical order in a series
	of or relating to a taxonomic order