lucidity vs understandability

lucidity and understandability both are nouns.

Word	Noun	Adjective	Verb	Adverb
lucidity	Yes	No	No	No
understandability	Yes	No	No	No

As nouns, understandability is a hypernym of lucidity; that is, understandability is a word with a broader meaning than lucidity:

lucidity: free from obscurity and easy to understand; the comprehensibility of clear expression
understandability: the quality of comprehensible language or thought

Other hypernyms of lucidity include comprehensibility.

lucidity (noun)	understandability (noun)
free from obscurity and easy to understand; the comprehensibility of clear expression	the quality of comprehensible language or thought
a lucid state of mind; not confused