ambiance vs gloominess

ambiance and gloominess both are nouns.

Word	Noun	Adjective	Verb	Adverb
ambiance	Yes	No	No	No
gloominess	Yes	No	No	No

As nouns, gloominess is a hyponym of ambiance; that is, gloominess is a word with a more specific, narrower meaning than ambiance:

Other hyponyms of ambiance include genius loci, gloom, glumness, miasm, miasma, feel, feeling, flavor, flavour, look, smell, spirit, tone, headiness.

ambiance (noun)	gloominess (noun)
the atmosphere of an environment	the quality of excessive mournfulness and uncheerfulness
a particular environment or surrounding influence	The property of having a frowning or scowling appearance.
	a feeling of melancholy apprehension
	an atmosphere of depression and melancholy