downheartedness vs lowness

downheartedness and lowness both are nouns.

Word	Noun	Adjective	Verb	Adverb
downheartedness	Yes	No	No	No
lowness	Yes	No	No	No

As nouns, downheartedness and lowness are synonyms defined as:

Other synonyms of downheartedness include dejectedness, dispiritedness, low-spiritedness.

downheartedness (noun)	lowness (noun)
a feeling of low spirits	the quality of being low; lacking height
	a low or small degree of any quality (amount or force or temperature etc.)
	a feeling of low spirits
	a position of inferior status; low in station or rank or fortune or estimation