ruggedness vs rugged

ruggedness is a noun but rugged is not a noun.

Word	Noun	Adjective	Verb	Adverb
ruggedness	Yes	No	No	No
rugged	No	Yes	No	No

ruggedness (noun)	rugged (noun)
the property of being big and strong
the quality of being topologically uneven
the quality of being difficult to do

ruggedness (adjective)	rugged (adjective)
	sturdy and strong in constitution or construction; enduring
	having long narrow shallow depressions (as grooves or wrinkles) in the surface
	very difficult; severely testing stamina or resolution
	topographically very uneven