This is the 1911th most frequent Spanish word.
os
"Os" is a pronoun in Spanish that means "to you" or "for you" (plural, informal).
In this sentence, 'os' is the informal second-person plural object pronoun used in Spain to address a group of people casually.
¿Os gustaría venir a la fiesta mañana?
Would you like to come to the party tomorrow?
Here, 'os' serves as the informal second-person plural direct object pronoun in Spain, indicating the recipient of the action of 'to tell.'
Siempre os digo que estudiéis bien.
I always tell you to study well.
'Os' in this sentence is the informal second-person plural indirect object pronoun in Spain, referring to the recipients of the congratulation.