OK… I waited in the hope an Arab native speaker would answer, but I guess I'll do it...
The singular is هللة which is transliterated either as “halalah” or “halala” (just like a Muslim girl, مسلمة, among British Muslims, is a “muslimah” or "muslima"). The plural is هللات which transliterates as “halalāt”.¹ But of course, if we use the word in English, we need to give it an English plural, which would normally be ending in “s”. This is exactly what this 25 halalas does.
So, standardize this way in English and French:
- singular: halala
- plural: halalas
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¹What complicates matters is the final consonant in the singular, ة, the “ta marbouta” (التاء المربوطة), which represents the sounds “h” and “t” at once. If you really want to know why, listen to this YT video from 7:56 where she pronounces words with an inflexion (…ta(n) / …tu(n) / …ti(n)) versus no inflection (…ah).
₱o$₮ag€ $₮am₱$ a₹€ mo₹€ £€₲i₮ima₮€ a$ a ƒo₹m oƒ ¢u₹₹€nc¥ ₮ha₦ ₮h€ €₦₮i₹€ "¢oi₦" ₱₹odu¢₮io₦ oƒ ₦au₹u o₹ ₦iu€. ••• £€$ ₮im฿₹€$-₱o$₮€ $o₦₮ ₱£u$ £é₲i₮im€$ €₦ ₮a₦t qu'o฿j€₮$ mo₦é₮ai₹€$ qu€ £a ₱₹odu¢₮io₦ €₦₮iè₹€ d€ «mo₦₦ai€$» d€ ₦au₹u ou d€ ₦iu€.