half-light vs visible light

half-light and visible light both are nouns.

Word	Noun	Adjective	Verb	Adverb
half-light	Yes	No	No	No
visible light	Yes	No	No	No

As nouns, visible light is a hypernym of half-light; that is, visible light is a word with a broader meaning than half-light:

half-light: a greyish light (as at dawn or dusk or in dim interiors)
visible light: (physics) electromagnetic radiation that can produce a visual sensation

Other hypernyms of half-light include light, visible radiation.

half-light (noun)	visible light (noun)
a greyish light (as at dawn or dusk or in dim interiors)	(physics) electromagnetic radiation that can produce a visual sensation