jewellery vs earring

jewellery and earring both are nouns.

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

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

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

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