Definition: A piece of jewelry worn on the lobe or edge of the ear.
Signing with one (generally in a casual register) or two hands (generally, a formal citation). When referred to one earring only (eg. male), say "one" + "earring". In this case, be specific which left or right if any culturally significant.
Formal citation; specifically referring to two earrings.
Stud earrings: a small piece of jewelry that is worn through a small hole in the earlobe.