drop earring vs earring

drop earring and earring both are nouns.

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

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

drop earring: an earring with a pendant ornament
earring: jewelry to ornament the ear; usually clipped to the earlobe or fastened through a hole in the lobe

drop earring (noun)	earring (noun)
an earring with a pendant ornament	jewelry to ornament the ear; usually clipped to the earlobe or fastened through a hole in the lobe