lightness vs weightlessness

lightness and weightlessness both are nouns.

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

As nouns, lightness and weightlessness are synonyms defined as:

lightness and weightlessness: the property of being comparatively small in weight

lightness (noun)	weightlessness (noun)
the trait of being lighthearted and frivolous	the property of being comparatively small in weight
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