Arabic Number to Words (Tafqeet)

The four rules that break naive converters

First, units come before tens. English says twenty-five. Arabic says خمسة وعشرون, five and twenty. Any converter that walks the digits left to right and joins the words produces عشرون وخمسة, which a bank clerk reads as wrong at a glance. Second, 3 to 10 take the opposite gender of the counted noun: ثلاثة جنيهات for a masculine noun, ثلاث ليرات for a feminine one. A converter that hard-codes ثلاثة is right for pounds and wrong for lira. Third, the counted noun changes form with the last two digits: 3 to 10 take the plural (ثلاثة آلاف), 11 to 99 take the singular accusative (أحد عشر ألفاً), and round hundreds and thousands take the plain singular (مائة جنيه, ألف جنيه). Fourth, the dual drops its nun before a noun: ألفان becomes ألفا ريال, and مائتان becomes مائتا ريال.

The scale words follow the same rules, because they are counted nouns too. ألف is masculine, so 3 thousands is ثلاثة آلاف, 11 thousands is أحد عشر ألفاً on its own and أحد عشر ألف ريال when the currency follows. مليون and مليار work the same way: ثلاثة ملايين, أحد عشر مليوناً, مليون ريال, مليونا ريال. The tool applies these rules to every group of the amount, then attaches the currency by the last-two-digits rule, so a large amount reads the way a cheque writer would write it.