protagonist vs pillar

protagonist and pillar both are nouns.

Word	Noun	Adjective	Verb	Adverb
protagonist	Yes	No	No	No
pillar	Yes	No	No	No

As nouns, pillar is a hyponym of protagonist; that is, pillar is a word with a more specific, narrower meaning than protagonist:

protagonist (noun)	pillar (noun)
a person who backs a politician or a team etc.	(architecture) a tall vertical cylindrical structure standing upright and used to support a structure
the principal character in a work of fiction	a vertical cylindrical structure standing alone and not supporting anything (such as a monument)
	a fundamental principle or practice
	a prominent supporter
	anything that approximates the shape of a column or tower