tiresome vs deadening

tiresome is not a noun while deadening is a noun.

Word	Noun	Adjective	Verb	Adverb
tiresome	No	Yes	No	No
deadening	Yes	Yes	No	No

As adjectives, tiresome and deadening are synonyms defined as:

tiresome and deadening: so lacking in interest as to cause mental weariness

Other synonyms of tiresome include boring, dull, ho-hum, irksome, slow, tedious, wearisome.

tiresome (noun)	deadening (noun)
	the act of making something futile and useless (as by routine)

tiresome (adjective)	deadening (adjective)
so lacking in interest as to cause mental weariness	so lacking in interest as to cause mental weariness