self-denial vs selflessness

self-denial and selflessness both are nouns.

Word	Noun	Adjective	Verb	Adverb
self-denial	Yes	No	No	No
selflessness	Yes	No	No	No

As nouns, selflessness is a hypernym of self-denial; that is, selflessness is a word with a broader meaning than self-denial:

self-denial: renunciation of your own interests in favor of the interests of others
selflessness: acting with less concern for yourself than for the success of the joint activity

Other hypernyms of self-denial include forgoing, forswearing, renunciation, self-sacrifice.

self-denial (noun)	selflessness (noun)
the act of denying yourself; controlling your impulses	acting with less concern for yourself than for the success of the joint activity
renunciation of your own interests in favor of the interests of others	the quality of unselfish concern for the welfare of others
the trait of practicing self discipline