obscurity vs semidarkness

obscurity and semidarkness both are nouns.

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

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

obscurity: the state of being indistinct or indefinite for lack of adequate illumination
semidarkness: partial darkness

obscurity (noun)	semidarkness (noun)
the quality of being unclear or abstruse and hard to understand	partial darkness
an obscure and unimportant standing; not well known
the state of being indistinct or indefinite for lack of adequate illumination