Which language was most widely used by the Achaemenid imperial bureaucracy?

While several languages were spoken across the Achaemenid Empire, Aramaic was the language most widely used in the imperial bureaucracy.12

Although Elamite served as a significant administrative language in regions such as Persis and Elam—as evidenced by the archives of clay tablets discovered at Persepolis—it was not the primary language of the broader imperial administration. Old Persian, while the language of the ruling Persians, was not a working written language for the empire's bureaucracy; it was primarily used for royal inscriptions, which were typically rendered in a trilingual format alongside Elamite and Akkadian.12