main vs chief

main and chief both are nouns.

Word	Noun	Adjective	Verb	Adverb
main	Yes	Yes	No	No
chief	Yes	Yes	No	No

As adjectives, main and chief are synonyms defined as:

Other synonyms of main include master, primary, principal.

main (noun)	chief (noun)
a principal pipe in a system that distributes water or gas or electricity or that collects sewage	a person who is in charge
any very large body of (salt) water	a person who exercises control over workers
	the head of a tribe or clan

main (adjective)	chief (adjective)
(of a clause) capable of standing syntactically alone as a complete sentence	most important element
most important element
of force; of the greatest possible intensity