dullness vs oscitance

dullness and oscitance both are nouns.

Word	Noun	Adjective	Verb	Adverb
dullness	Yes	No	No	No
oscitance	Yes	No	No	No

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

Other hyponyms of dullness include oscitancy.

dullness (noun)	oscitance (noun)
lack of sensibility	an involuntary intake of breath through a wide open mouth; usually triggered by fatigue or boredom
without sharpness or clearness of edge or point	drowsiness and dullness manifested by yawning
the quality of lacking interestingness
a lack of visual brightness
the quality of being slow to understand