low-spiritedness vs unhappiness

low-spiritedness and unhappiness both are nouns.

Word	Noun	Adjective	Verb	Adverb
low-spiritedness	Yes	No	No	No
unhappiness	Yes	No	No	No

As nouns, unhappiness is a hypernym of low-spiritedness; that is, unhappiness is a word with a broader meaning than low-spiritedness:

Other hypernyms of low-spiritedness include sadness.

low-spiritedness (noun)	unhappiness (noun)
a feeling of low spirits	emotions experienced when not in a state of well-being
	state characterized by emotions ranging from mild discontentment to deep grief