jewellery vs adornment

jewellery and adornment both are nouns.

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

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

jewellery: an adornment (as a bracelet or ring or necklace) made of precious metals and set with gems (or imitation gems)
adornment: a decoration of color or interest that is added to relieve plainness

jewellery (noun)	adornment (noun)
an adornment (as a bracelet or ring or necklace) made of precious metals and set with gems (or imitation gems)	the action of decorating yourself with something colorful and interesting
	a decoration of color or interest that is added to relieve plainness