This is the 4682nd most frequent Portuguese word.
diga
"Say" or "tell" (imperative form of "dizer").
In this sentence, 'diga' is used as an imperative form of the verb 'dizer' to make a polite request or command, asking someone to inform the speaker.
Diga-me onde está o livro.
Tell me where the book is.
Here, 'diga' serves as an imperative to instruct the addressee to transmit a message, expressing a polite direction.
Por favor, diga ao João que a reunião foi cancelada.
Please tell João that the meeting has been canceled.
In this usage, 'diga' is part of a conditional sentence, providing instructions on what to say based on a specific situation.