main line vs path

main line and path both are nouns.

Word	Noun	Adjective	Verb	Adverb
main line	Yes	No	No	No
path	Yes	No	No	No

As nouns, path is a hypernym of main line; that is, path is a word with a broader meaning than main line:

Other hypernyms of main line include itinerary, route.

main line (noun)	path (noun)
the principal route of a transportation system	a course of conduct
	a way especially designed for a particular use
	an established line of travel or access
	a line or route along which something travels or moves