colloquialism vs umteenth

colloquialism is a noun but umteenth is not a noun.

Word	Noun	Adjective	Verb	Adverb
colloquialism	Yes	No	No	No
umteenth	No	Yes	No	No

colloquialism (noun)	umteenth (noun)
a colloquial expression; characteristic of spoken or written communication that seeks to imitate informal speech

colloquialism (adjective)	umteenth (adjective)
	last in an indefinitely numerous series