Imperial Aramaic was highly standardised; its orthography was based more on historical roots than any spoken dialect, and the inevitable influence of Old Persian gave the language a new clarity and robust flexibility. For centuries after the fall of the Achaemenid Empire (in 331 BCE), Imperial Aramaic or a similar dialect would remain an influence on the various native Iranian languages. Aramaic script and, as ideograms, Aramaic vocabulary would survive as the essential characteristics of the Pahlavi scripts.[11]