gloom vs apprehension

gloom and apprehension both are nouns.

Word	Noun	Adjective	Verb	Adverb
gloom	Yes	No	No	No
apprehension	Yes	No	No	No

As nouns, apprehension is a hypernym of gloom; that is, apprehension is a word with a broader meaning than gloom:

Other hypernyms of gloom include apprehensiveness, dread, melancholy.

gloom (noun)	apprehension (noun)
a feeling of melancholy apprehension	the act of apprehending (especially apprehending a criminal)
a state of partial or total darkness	the cognitive condition of someone who understands
an atmosphere of depression and melancholy	painful expectation
	fearful expectation or anticipation