graveness vs seriousness

graveness and seriousness both are nouns.

Word	Noun	Adjective	Verb	Adverb
graveness	Yes	No	No	No
seriousness	Yes	No	No	No

As nouns, seriousness is a hypernym of graveness; that is, seriousness is a word with a broader meaning than graveness:

Other hypernyms of graveness include earnestness, serious-mindedness, sincerity.

graveness (noun)	seriousness (noun)
a manner that is serious and solemn	the trait of being serious
	the quality of arousing fear or distress
	an earnest and sincere feeling