selflessness vs self-sacrifice

selflessness and self-sacrifice both are nouns.

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

As nouns, selflessness and self-sacrifice are synonyms defined as:

selflessness and self-sacrifice: acting with less concern for yourself than for the success of the joint activity

selflessness (noun)	self-sacrifice (noun)
acting with less concern for yourself than for the success of the joint activity	acting with less concern for yourself than for the success of the joint activity
the quality of unselfish concern for the welfare of others