oscitancy vs sleepiness

oscitancy and sleepiness both are nouns.

Word	Noun	Adjective	Verb	Adverb
oscitancy	Yes	No	No	No
sleepiness	Yes	No	No	No

As nouns, sleepiness is a hypernym of oscitancy; that is, sleepiness is a word with a broader meaning than oscitancy:

Other hypernyms of oscitancy include dullness, obtuseness, drowsiness, somnolence.

oscitancy (noun)	sleepiness (noun)
an involuntary intake of breath through a wide open mouth; usually triggered by fatigue or boredom	a very sleepy state
drowsiness and dullness manifested by yawning