cufflink vs jewellery

cufflink and jewellery both are nouns.

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

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

cufflink: jewelry consisting of one of a pair of linked buttons used to fasten the cuffs of a shirt
jewellery: an adornment (as a bracelet or ring or necklace) made of precious metals and set with gems (or imitation gems)

Other hypernyms of cufflink include jewelry.

cufflink (noun)	jewellery (noun)
jewelry consisting of one of a pair of linked buttons used to fasten the cuffs of a shirt	an adornment (as a bracelet or ring or necklace) made of precious metals and set with gems (or imitation gems)