unevenness vs unregularity

unevenness and unregularity both are nouns.

Word	Noun	Adjective	Verb	Adverb
unevenness	Yes	No	No	No
unregularity	Yes	No	No	No

As nouns, unregularity is a hypernym of unevenness; that is, unregularity is a word with a broader meaning than unevenness:

unevenness: the quality of being uneven and lacking uniformity
unregularity: not characterized by a fixed principle or rate; at irregular intervals

Other hypernyms of unevenness include irregularity.

unevenness (noun)	unregularity (noun)
the quality of being uneven and lacking uniformity	not characterized by a fixed principle or rate; at irregular intervals
the quality of being unbalanced