sheet vs cover

sheet and cover both are nouns.

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

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

sheet (noun)	cover (noun)
bed linen consisting of a large rectangular piece of cotton or linen cloth; used in pairs	the act of concealing the existence of something by obstructing the view of it
(nautical) a line (rope or chain) that regulates the angle at which a sail is set in relation to the wind	fire that makes it difficult for the enemy to fire on your own individuals or formations
a flat artifact that is thin relative to its length and width	a false identity and background (especially one created for an undercover agent)
a large piece of fabric (usually canvas fabric) by means of which wind is used to propel a sailing vessel	a recording of a song that was first recorded or made popular by somebody else
paper used for writing or printing	bedding that keeps a person warm in bed
newspaper with half-size pages	a covering that serves to conceal or shelter something
any broad thin expanse or surface	covering for a hole (especially a hole in the top of a container)
(mathematics) an unbounded two-dimensional shape	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

sheet (verb)	cover (verb)
cover with a sheet, as if by wrapping	sit on (eggs)
come down as if in sheets	clothe, as if for protection from the elements
	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