lightness vs nimbus

lightness and nimbus both are nouns.

Word	Noun	Adjective	Verb	Adverb
lightness	Yes	No	No	No
nimbus	Yes	No	No	No

As nouns, nimbus is a hyponym of lightness; that is, nimbus is a word with a more specific, narrower meaning than lightness:

lightness: the visual effect of illumination on objects or scenes as created in pictures
nimbus: an indication of radiant light drawn around the head of a saint

Other hyponyms of lightness include aura, aureole, gloriole, glory, halo, sunniness, highlight, highlighting, brightness.

lightness (noun)	nimbus (noun)
the trait of being lighthearted and frivolous	an indication of radiant light drawn around the head of a saint
the visual effect of illumination on objects or scenes as created in pictures	a dark grey cloud bearing rain
the property of being comparatively small in weight
having a light color
the gracefulness of a person or animal that is quick and nimble
a feeling of joy and pride