main vs electric main

main and electric main both are nouns.

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

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

main: a principal pipe in a system that distributes water or gas or electricity or that collects sewage
electric main: a main that distributes electricity

Other hyponyms of main include gas main, sewer line, sewer main, water main.

main (noun)	electric main (noun)
a principal pipe in a system that distributes water or gas or electricity or that collects sewage	a main that distributes electricity
any very large body of (salt) water

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