endless vs endlessness

endless is not a noun while endlessness is a noun.

Word	Noun	Adjective	Verb	Adverb
endless	No	Yes	No	No
endlessness	Yes	No	No	No

endless (noun)	endlessness (noun)
	the property of being (or seeming to be) without end

endless (adjective)	endlessness (adjective)
having the ends united so as to form a continuous whole
having no known beginning and presumably no end
tiresomely long; seemingly without end
infinitely great in number