melancholic vs melancholy

melancholic and melancholy both are nouns.

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

As adjectives, melancholic and melancholy are synonyms defined as:

melancholic and melancholy: characterized by or causing or expressing sadness

melancholic (noun)	melancholy (noun)
someone subject to melancholia	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

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