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"Once" is a form of "once", an adjective which is often translated as "eleven". "Treinta" is a noun which is often translated as "thirty". Learn more about the difference between "treinta" and "once" below.
el treinta(
treyn
-
tah
)A masculine noun is used with masculine articles and adjectives (e.g., el hombre guapo, el sol amarillo).
2. (number)
b. thirtieth (in dates)
El cumpleaños de mi padre es el treinta de noviembre.My father’s birthday is on the thirtieth of November.
once(
ohn
-
seh
)An adjective is a word that describes a noun (e.g., the big dog).
A masculine noun is used with masculine articles and adjectives (e.g., el hombre guapo, el sol amarillo).
2. (number)
3. (sports)
a. first team
El entrenador no anunció cambios en el once titular para esta temporada.The coach didn't announce any changes to the first team for this season.
los onces
A plural noun indicates that there is more than one person, place, thing, or idea.