perilousness vs danger

perilousness and danger both are nouns.

Word	Noun	Adjective	Verb	Adverb
perilousness	Yes	No	No	No
danger	Yes	No	No	No

As nouns, danger is a hypernym of perilousness; that is, danger is a word with a broader meaning than perilousness:

perilousness (noun)	danger (noun)
the state of being dangerous	a venture undertaken without regard to possible loss or injury
	a dangerous place
	the condition of being susceptible to harm or injury
	a cause of pain or injury or loss