friend vs pillar

friend and pillar both are nouns.

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

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

friend (noun)	pillar (noun)
a person you know well and regard with affection and trust	(architecture) a tall vertical cylindrical structure standing upright and used to support a structure
a person with whom you are acquainted	a vertical cylindrical structure standing alone and not supporting anything (such as a monument)
an associate who provides cooperation or assistance	a fundamental principle or practice
a person who backs a politician or a team etc.	a prominent supporter
	anything that approximates the shape of a column or tower