foil vs cover

foil and cover both are nouns.

Word	Noun	Adjective	Verb	Adverb
foil	Yes	No	Yes	No
cover	Yes	No	Yes	No

As verbs, cover is a hypernym of foil; that is, cover is a word with a broader meaning than foil:

foil (noun)	cover (noun)
a light slender flexible sword tipped by a button	the act of concealing the existence of something by obstructing the view of it
a piece of thin and flexible sheet metal	fire that makes it difficult for the enemy to fire on your own individuals or formations
picture consisting of a positive photograph or drawing on a transparent base; viewed with a projector	a false identity and background (especially one created for an undercover agent)
a device consisting of a flat or curved piece (as a metal plate) so that its surface reacts to the water it is passing through	a recording of a song that was first recorded or made popular by somebody else
anything that serves by contrast to call attention to another thing's good qualities	bedding that keeps a person warm in bed
	a covering that serves to conceal or shelter something
	covering for a hole (especially a hole in the top of a container)
	the protective covering on the front, back, and spine of a book
	a natural object that covers or envelops
	a fixed charge by a restaurant or nightclub over and above the charge for food and drink

foil (verb)	cover (verb)
cover or back with foil	sit on (eggs)
hinder or prevent (the efforts, plans, or desires) of	clothe, as if for protection from the elements
enhance by contrast	protect by insurance
	act on verbally or in some form of artistic expression
	be responsible for reporting the details of, as in journalism
	maintain a check on; especially by patrolling
	protect or defend (a position in a game)
	hold within range of an aimed firearm
	play a higher card than the one previously played
	be responsible for guarding an opponent in a game
	provide with a covering or cause to be covered
	form a cover over
	copulate with a female, used especially of horses
	cover as if with a shroud
	put something on top of something else
	travel across or pass over
	hide from view or knowledge
	spread over a surface to conceal or protect
	be sufficient to meet, defray, or offset the charge or cost of
	to take an action to protect against future problems
	invest with a large or excessive amount of something
	help out by taking someone's place and temporarily assuming his responsibilities
	provide for
	span an interval of distance, space or time
	include in scope; include as part of something broader; have as one's sphere or territory
	make up for shortcomings or a feeling of inferiority by exaggerating good qualities