niqab vs face veil

niqab and face veil both are nouns.

Word	Noun	Adjective	Verb	Adverb
niqab	Yes	No	No	No
face veil	Yes	No	No	No

As nouns, face veil is a hypernym of niqab; that is, face veil is a word with a broader meaning than niqab:

niqab: a face veil covering the lower part of the face (up to the eyes) worn by observant Muslim women
face veil: a piece of more-or-less transparent material that covers the face

niqab (noun)	face veil (noun)
a face veil covering the lower part of the face (up to the eyes) worn by observant Muslim women	a piece of more-or-less transparent material that covers the face