oscitancy vs somnolence

oscitancy and somnolence both are nouns.

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

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

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

oscitancy (noun)	somnolence (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