submenu vs menu

submenu and menu both are nouns.

Word	Noun	Adjective	Verb	Adverb
submenu	Yes	No	No	No
menu	Yes	No	No	No

As nouns, menu is a hypernym of submenu; that is, menu is a word with a broader meaning than submenu:

submenu: a secondary menu that appears while you are holding the cursor over an item on the primary menu
menu: (computer science) a list of options available to a computer user

Other hypernyms of submenu include computer menu.

submenu (noun)	menu (noun)
a secondary menu that appears while you are holding the cursor over an item on the primary menu	an agenda of things to do
	a list of dishes available at a restaurant
	(computer science) a list of options available to a computer user
	the dishes making up a meal