joyfulness vs lightness

joyfulness and lightness both are nouns.

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

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

joyfulness (noun)	lightness (noun)
the emotion of great happiness	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