head covering vs chador

head covering and chador both are nouns.

Word	Noun	Adjective	Verb	Adverb
head covering	Yes	No	No	No
chador	Yes	No	No	No

As nouns, chador is a hyponym of head covering; that is, chador is a word with a more specific, narrower meaning than head covering:

head covering: a garment that covers the head and face
chador: a cloth used as a head covering (and veil and shawl) by Muslim and Hindu women

Other hyponyms of head covering include chadar, chaddar, chuddar, face veil, yashmac, yashmak.

head covering (noun)	chador (noun)
a garment that covers the head and face	a cloth used as a head covering (and veil and shawl) by Muslim and Hindu women