This is the 12869th most frequent Portuguese word.
vosso
"Vosso" means "your" (plural, formal or informal) in English, referring to possession by multiple people.
"Vosso" here is used as a possessive pronoun to indicate that the book belongs to 'you all' in a formal context.
Este é o vosso livro que foi esquecido na mesa.
This is your book that was forgotten on the table.
Used as a possessive adjective modifying 'day,' indicating the day of a group addressed formally as 'you all.'
Espero que o vosso dia esteja indo bem.
I hope your day is going well.
Reflects possession of work done by the plural and formal 'you all.'