egoism vs self-interest

egoism and self-interest both are nouns.

Word	Noun	Adjective	Verb	Adverb
egoism	Yes	No	No	No
self-interest	Yes	No	No	No

As nouns, egoism and self-interest are synonyms defined as:

Other synonyms of egoism include egocentrism, self-centeredness, self-concern.

egoism (noun)	self-interest (noun)
concern for your own interests and welfare	concern for your own interests and welfare
(ethics) the theory that the pursuit of your own welfare is the basis of morality	taking advantage of opportunities without regard for the consequences for others