senselessness vs senseless

senselessness is a noun but senseless is not a noun.

Word	Noun	Adjective	Verb	Adverb
senselessness	Yes	No	No	No
senseless	No	Yes	No	No

senselessness (noun)	senseless (noun)
total lack of meaning or ideas

senselessness (adjective)	senseless (adjective)
	(of especially persons) lacking sense or understanding or judgment
	unresponsive to stimulation
	not marked by the use of reason
	serving no useful purpose; having no excuse for being