sheath vs scabbard

sheath and scabbard both are nouns.

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

As nouns, scabbard is a hyponym of sheath; that is, scabbard is a word with a more specific, narrower meaning than sheath:

Other hyponyms of sheath include aglet, aiglet, cot, fingerstall, holster.

sheath (noun)	scabbard (noun)
a protective covering (as for a knife or sword)	a sheath for a sword or dagger or bayonet
a dress suitable for formal occasions
an enveloping structure or covering enclosing an animal or plant organ or part