obtuseness vs dullness

obtuseness and dullness both are nouns.

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

As nouns, dullness is a hypernym of obtuseness; that is, dullness is a word with a broader meaning than obtuseness:

Other hypernyms of obtuseness include bluntness.

As nouns, obtuseness and dullness are synonyms defined as:

obtuseness (noun)	dullness (noun)
the quality of lacking a sharp edge or point	lack of sensibility
the quality of being slow to understand	without sharpness or clearness of edge or point
	the quality of lacking interestingness
	a lack of visual brightness
	the quality of being slow to understand