custom vs hijab

custom and hijab both are nouns.

Word	Noun	Adjective	Verb	Adverb
custom	Yes	Yes	No	No
hijab	Yes	No	No	No

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

custom: accepted or habitual practice
hijab: the custom in some Islamic societies of women dressing modestly outside the home

Other hyponyms of custom include Americanism, Anglicism, Britishism, consuetude, couvade, Germanism, habit, use, rite, ritual.

custom (noun)	hijab (noun)
accepted or habitual practice	the custom in some Islamic societies of women dressing modestly outside the home
habitual patronage	a headscarf worn by Muslim women; conceals the hair and neck and usually has a face veil that covers the face
a specific practice of long standing
money collected under a tariff

custom (adjective)	hijab (adjective)
made according to the specifications of an individual