Arete vs. aro vs. pendiente vs. zarcillo

The Spanish words 'arete', 'aro', 'pendiente', and 'zarcillo' all refer to 'earring'. However, their usage varies depending on the countries, regions, and contexts within the Spanish-speaking world.

Arete

In some Spanish-speaking countries, such as Mexico and Central America, 'arete' is a common term for earring.
Me compré unos aretes de plata.
(I bought some silver earrings.)

Aro

'Aro' literally translates to 'hoop' in English. It can refer specifically to hoop earrings, but in some contexts and regions such as Chile and Argentina, it's used more generally to mean any type of earring.
Ella usa aros grandes.
(She wears large hoop earrings.)
Voy a comprarme un par de aros nuevos.
(I'm going to buy myself a new pair of earrings.)

Pendiente

'Pendiente' is commonly used in Spain and refers to any type of earring. It is derived from the verb 'pendere', meaning 'to hang down', which indicates the function of an earring to hang down from the ear.
He perdido un pendiente de diamante.
(I've lost a diamond earring.)
Ella lleva pendientes largos y brillantes.
(She wears long, shiny earrings.)

Zarcillo

'Zarcillo' means vinery or tendril in general. In Venezuela and some other regions it's often used to indicate earring. The word likely developed this meaning because certain types of earrings have designs that resemble vine tendrils.
Me encanta tu zarcillo, ¿dónde lo compraste?
(I love your earring, where did you buy it?)
Ella lleva unos zarcillos coloridos y atractivos.
(She wears colorful and attractive earrings.)

Summary

All four terms are synonyms for 'earring' within different parts of the Spanish-speaking world. The use of each term depends on regional preferences. For example, 'arete' is commonly used in Central America and Mexico while Spaniards prefer 'pendiente'. The term 'aro' usually refers specifically to hoop earrings but can denote any earring in countries like Chile and Argentina. Lastly, 'zarcillo', evokes imagery of tendrils or vines due its literal meaning and is popularly used for describing earrings in Venezuela.