skullcap vs yarmulke

skullcap and yarmulke both are nouns.

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

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

Other hyponyms of skullcap include beanie, beany, coif, yarmelke, yarmulka.

skullcap (noun)	yarmulke (noun)
rounded brimless cap fitting the crown of the head	a skullcap worn by religious Jews (especially at prayer)
the dome of the skull
a herbaceous plant of the genus Scutellaria which has a calyx that, when inverted, resembles a helmet with its visor raised