clumsiness vs stiffness

clumsiness and stiffness both are nouns.

Word	Noun	Adjective	Verb	Adverb
clumsiness	Yes	No	No	No
stiffness	Yes	No	No	No

As nouns, stiffness is a hyponym of clumsiness; that is, stiffness is a word with a more specific, narrower meaning than clumsiness:

clumsiness: the carriage of someone whose movements and posture are ungainly or inelegant
stiffness: the property of moving with pain or difficulty

Other hyponyms of clumsiness include gracelessness, ungracefulness, gawkiness, ungainliness.

As nouns, clumsiness and stiffness are synonyms defined as:

clumsiness and stiffness: the inelegance of someone stiff and unrelaxed (as by embarrassment)

Other synonyms of clumsiness include awkwardness, gracelessness.

clumsiness (noun)	stiffness (noun)
the carriage of someone whose movements and posture are ungainly or inelegant	the physical property of being inflexible and hard to bend
the inelegance of someone stiff and unrelaxed (as by embarrassment)	the property of moving with pain or difficulty
unskillfulness resulting from a lack of training	the inelegance of someone stiff and unrelaxed (as by embarrassment)
	excessive sternness
	firm resoluteness in purpose or opinion or action