heavyheartedness vs melancholy

heavyheartedness and melancholy both are nouns.

Word	Noun	Adjective	Verb	Adverb
heavyheartedness	Yes	No	No	No
melancholy	Yes	Yes	No	No

As nouns, melancholy is a hypernym of heavyheartedness; that is, melancholy is a word with a broader meaning than heavyheartedness:

heavyheartedness (noun)	melancholy (noun)
a feeling of dispirited melancholy	a humor that was once believed to be secreted by the kidneys or spleen and to cause sadness and melancholy
	a feeling of thoughtful sadness
	a constitutional tendency to be gloomy and depressed

heavyheartedness (adjective)	melancholy (adjective)
	grave or even gloomy in character
	characterized by or causing or expressing sadness