egotism vs self-importance

egotism and self-importance both are nouns.

Word	Noun	Adjective	Verb	Adverb
egotism	Yes	No	No	No
self-importance	Yes	No	No	No

As nouns, egotism and self-importance are synonyms defined as:

egotism and self-importance: an exaggerated opinion of your own importance

Other synonyms of egotism include swelled head.

As nouns, egotism and self-importance are synonyms defined as:

egotism and self-importance: an inflated feeling of pride in your superiority to others

Other synonyms of egotism include ego.

egotism (noun)	self-importance (noun)
an exaggerated opinion of your own importance	an exaggerated opinion of your own importance
an inflated feeling of pride in your superiority to others	an inflated feeling of pride in your superiority to others