irrelevant vs moot

irrelevant is not a noun while moot is a noun.

Word	Noun	Adjective	Verb	Adverb
irrelevant	No	Yes	No	No
moot	Yes	Yes	Yes	No

irrelevant (noun)	moot (noun)
	a hypothetical case that law students argue as an exercise

irrelevant (adjective)	moot (adjective)
having no bearing on or connection with the subject at issue	open to argument or debate
	of no legal significance (as having been previously decided)

irrelevant (verb)	moot (verb)
	think about carefully; weigh