studiousness vs diligence

studiousness and diligence both are nouns.

Word	Noun	Adjective	Verb	Adverb
studiousness	Yes	No	No	No
diligence	Yes	No	No	No

As nouns, diligence is a hypernym of studiousness; that is, diligence is a word with a broader meaning than studiousness:

Other hypernyms of studiousness include industriousness, industry.

studiousness (noun)	diligence (noun)
diligent study	a diligent effort
	persevering determination to perform a task
	conscientiousness in paying proper attention to a task; giving the degree of care required in a given situation