ordinal vs fifty-fifth

ordinal is a noun but fifty-fifth is not a noun.

Word	Noun	Adjective	Verb	Adverb
ordinal	Yes	Yes	No	No
fifty-fifth	No	Yes	No	No

ordinal (noun)	fifty-fifth (noun)
the number designating place in an ordered sequence

ordinal (adjective)	fifty-fifth (adjective)
being or denoting a numerical order in a series	the ordinal number of fifty-five in counting order
of or relating to a taxonomic order