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The replacement of the Pahlavi scripts with the Persian alphabet to write the Persian language was done by the Saffarid dynasty and Samanid dynasty in 9th-century Greater Khorasan. It is mostly but not exclusively right-to-left; mathematical expressions, numeric dates and numbers bearing units are embedded from left to right. The script is cursive, meaning most letters in a word connect to each other; when they are typed, contemporary word processors automatically join adjacent letter forms.