territorial waters vs main

territorial waters and main both are nouns.

Word	Noun	Adjective	Verb	Adverb
territorial waters	Yes	No	No	No
main	Yes	Yes	No	No

territorial waters (noun)	main (noun)
the waters surrounding a nation and its territories over which that nation exercises sovereign jurisdiction	a principal pipe in a system that distributes water or gas or electricity or that collects sewage
	any very large body of (salt) water

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