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"El" is a form of "el", a definite article which is often translated as "the". "Los domingos" is a form of "los domingos", a phrase which is often translated as "Sundays". Learn more about the difference between "el" and "los domingos" below.
el(
ehl
)A definite article is a word that identifies a noun as specific or known to the speaker (e.g., the girl).
los domingos
A phrase is a group of words commonly used together (e.g., once upon a time).
a. Sundays
Para mí, los domingos son aburridos porque no veo a nadie.I find Sundays boring because I don't see anyone.
b. the Sundays
Los domingos que no tengo partido, me quedo en la cama hasta tarde.The Sundays we don't have a game, I have a lie-in.
b. every Sunday
Los domingos vamos a almorzar con mis abuelos.We go to my grandparents' for lunch every Sunday.
c. Sundays
¿Y los domingos? ¿Qué sueles hacer por la tarde?What about Sundays? What do you tend to do in the afternoon?