QUICK ANSWER
"Alhajas" is a form of "alhajas", a plural noun which is often translated as "jewelry". "Joya" is a noun which is often translated as "piece of jewelry". Learn more about the difference between "alhajas" and "joya" below.
las alhajas(
ahl
-
ah
-
hahs
)A plural noun indicates that there is more than one person, place, thing, or idea.
a. jewelry (United States)
Regionalism used in the United States
El marido de Ángeles le regaló unas alhajas preciosas por su primer aniversario de boda.Angeles' husband gave her some beautiful jewelry for their first wedding anniversary.
b. jewellery (United Kingdom)
Regionalism used in the United Kingdom
La modelo ha lanzado su propia línea de alhajas de fantasía que está teniendo mucho éxito.The model has launched her own costume-jewellery line which is proving very successful.
la alhaja
A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).
a. precious object
El museo recibió nuevas pinturas y alhajas.The museum received new paintings and precious objects.
b. treasure
La alhaja que se llevaron valía un millón de pesos.The treasure that was stolen was worth a million pesos.
a. gem
El catedrático Musso es una alhaja. Es un honor tener a un profesor tan prestigioso en nuestra facultad.Professor Musso is a gem. It's an honor to have such a prestigious professor in our faculty.
b. treasure
¡La prometida de mi hijo es una alhaja! Me alegra muchísimo que se vayan a casar.My son's fiancée is a treasure! I'm really happy they're getting married.
la joya(
hoh
-
yah
)A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).
1. (ornament)
a. piece of jewelry (United States)
Regionalism used in the United States
Empeñé mi reloj y una joya.I pawned my watch and a piece of jewelry.
b. piece of jewellery (United Kingdom)
Regionalism used in the United Kingdom
El tasador dijo que esta joya vale $20,000.The assessor said this piece of jewellery is worth $20,000.
c. gem
La duquesa guarda todas sus joyas en la caja fuerte.The duchess keeps all her gems in the safe.