alcove vs niche

alcove and niche both are nouns.

Word	Noun	Adjective	Verb	Adverb
alcove	Yes	No	No	No
niche	Yes	No	No	No

As nouns, niche is a hypernym of alcove; that is, niche is a word with a broader meaning than alcove:

Other hypernyms of alcove include recess.

alcove (noun)	niche (noun)
a small recess opening off a larger room	an enclosure that is set back or indented
	a small concavity
	a position particularly well suited to the person who or organization which occupies it
	(ecology) the status of an organism within its environment and community (affecting its survival as a species)