This is the 13402nd most frequent Spanish word.
recibidas
"Received."
In this sentence, 'recibidas' is used as a past participle of the verb 'recibir', functioning as an adjective that describes the noun 'cartas'.
Las cartas recibidas ayer ya fueron revisadas.
The letters received yesterday have already been reviewed.
Here, 'recibidas' also acts as a past participle, describing 'palabras de ánimo,' indicating the reception of these words in the past.
Las palabras de ánimo recibidas durante la reunión fueron muy motivadoras.
The words of encouragement received during the meeting were very motivating.
Similarly, 'recibidas' modifies 'respuestas,' specifying that these were received from participants.