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"Os" is a pronoun which is often translated as "you", and "los" is a definite article which is often translated as "the". Learn more about the difference between "os" and "los" below.
os(
ohs
)A pronoun is a word that stands in for a noun (e.g., she).
a. you
Os quiero mucho, chicos. Voy a echaros mucho de menos.I really love you, guys. I'll miss you a lot.
a. you
¿Quién os dio entradas de primera fila para el concierto?Who gave you front-row tickets to the concert?
a. yourselves
Os vais a lastimar si seguís jugando con esa rama.You're going to hurt yourselves if you keep playing with that stick.
los(
lohs
)A definite article is a word that identifies a noun as specific or known to the speaker (e.g., the girl).
A pronoun is a word that stands in for a noun (e.g., she).