shadiness vs semidarkness

shadiness and semidarkness both are nouns.

Word	Noun	Adjective	Verb	Adverb
shadiness	Yes	No	No	No
semidarkness	Yes	No	No	No

As nouns, semidarkness is a hypernym of shadiness; that is, semidarkness is a word with a broader meaning than shadiness:

shadiness: relative darkness caused by light rays being intercepted by an opaque body
semidarkness: partial darkness

shadiness (noun)	semidarkness (noun)
questionable honesty or legality	partial darkness
relative darkness caused by light rays being intercepted by an opaque body