bijou vs jewelry

bijou and jewelry both are nouns.

Word	Noun	Adjective	Verb	Adverb
bijou	Yes	No	No	No
jewelry	Yes	No	No	No

As nouns, jewelry is a hypernym of bijou; that is, jewelry is a word with a broader meaning than bijou:

bijou: a small and delicately worked piece
jewelry: an adornment (as a bracelet or ring or necklace) made of precious metals and set with gems (or imitation gems)

Other hypernyms of bijou include jewellery.

bijou (noun)	jewelry (noun)
a small and delicately worked piece	an adornment (as a bracelet or ring or necklace) made of precious metals and set with gems (or imitation gems)