skullcap vs os

skullcap and os both are nouns.

Word	Noun	Adjective	Verb	Adverb
skullcap	Yes	No	No	No
os	Yes	No	No	No

As nouns, os is a hypernym of skullcap; that is, os is a word with a broader meaning than skullcap:

Other hypernyms of skullcap include bone.

skullcap (noun)	os (noun)
rounded brimless cap fitting the crown of the head	rigid connective tissue that makes up the skeleton of vertebrates
the dome of the skull	a mouth or mouthlike opening
a herbaceous plant of the genus Scutellaria which has a calyx that, when inverted, resembles a helmet with its visor raised