ponderousness vs ponderous

ponderousness is a noun but ponderous is not a noun.

Word	Noun	Adjective	Verb	Adverb
ponderousness	Yes	No	No	No
ponderous	No	Yes	No	No

ponderousness (noun)	ponderous (noun)
the property of being large in mass
an oppressive quality that is laborious and solemn and lacks grace or fluency

ponderousness (adjective)	ponderous (adjective)
	slow and laborious because of weight
	having great mass and weight and unwieldiness
	labored and dull