selflessness vs altruism

selflessness and altruism both are nouns.

Word	Noun	Adjective	Verb	Adverb
selflessness	Yes	No	No	No
altruism	Yes	No	No	No

As nouns, selflessness and altruism are synonyms defined as:

selflessness and altruism: the quality of unselfish concern for the welfare of others

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