main clause vs clause

main clause and clause both are nouns.

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

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

main clause: a clause in a complex sentence that can stand alone as a complete sentence
clause: (grammar) an expression including a subject and predicate functioning as a part of a complex sentence

main clause (noun)	clause (noun)
a clause in a complex sentence that can stand alone as a complete sentence	(grammar) an expression including a subject and predicate functioning as a part of a complex sentence
	a separate section of a legal document (as a statute or contract or will)