holster vs sheath

holster and sheath both are nouns.

Word	Noun	Adjective	Verb	Adverb
holster	Yes	No	No	No
sheath	Yes	No	No	No

As nouns, sheath is a hypernym of holster; that is, sheath is a word with a broader meaning than holster:

holster (noun)	sheath (noun)
a sheath (usually leather) for carrying a handgun	a protective covering (as for a knife or sword)
a belt with loops or slots for carrying small hand tools	a dress suitable for formal occasions
	an enveloping structure or covering enclosing an animal or plant organ or part