earring vs jewellery

earring and jewellery both are nouns.

Word	Noun	Adjective	Verb	Adverb
earring	Yes	No	No	No
jewellery	Yes	No	No	No

As nouns, jewellery is a hypernym of earring; that is, jewellery is a word with a broader meaning than earring:

earring: jewelry to ornament the ear; usually clipped to the earlobe or fastened through a hole in the lobe
jewellery: an adornment (as a bracelet or ring or necklace) made of precious metals and set with gems (or imitation gems)

Other hypernyms of earring include jewelry.

earring (noun)	jewellery (noun)
jewelry to ornament the ear; usually clipped to the earlobe or fastened through a hole in the lobe	an adornment (as a bracelet or ring or necklace) made of precious metals and set with gems (or imitation gems)