lightness vs high spirits

lightness and high spirits both are nouns.

Word	Noun	Adjective	Verb	Adverb
lightness	Yes	No	No	No
high spirits	Yes	No	No	No

As nouns, lightness and high spirits are synonyms defined as:

Other synonyms of lightness include elation.

lightness (noun)	high spirits (noun)
the trait of being lighthearted and frivolous	a feeling of joy and pride
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