niche vs mihrab

niche and mihrab both are nouns.

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

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

niche: an enclosure that is set back or indented
mihrab: (Islam) a niche in the wall of a mosque that indicates the direction of Mecca

Other hyponyms of niche include alcove, bay, apse, apsis, cinerarium, columbarium, fireplace, hearth, open fireplace.

niche (noun)	mihrab (noun)
an enclosure that is set back or indented	(Islam) a niche in the wall of a mosque that indicates the direction of Mecca
a small concavity	(Islam) a design in the shape of niche in a Muslim prayer rug; during worship the niche must be pointed toward Mecca
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)