highlighting vs lightness

highlighting and lightness both are nouns.

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

As nouns, lightness is a hypernym of highlighting; that is, lightness is a word with a broader meaning than highlighting:

highlighting: an area of lightness in a picture
lightness: the visual effect of illumination on objects or scenes as created in pictures

Other hypernyms of highlighting include light.

highlighting (noun)	lightness (noun)
an area of lightness in a picture	the trait of being lighthearted and frivolous
	the visual effect of illumination on objects or scenes as created in pictures
	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