ث ل ثth-l-th
— ثَلَاثthalāth / ثَلَاثَةthalāthah: the number three. This root occurs 32 times in the Quran, in various forms. ﴿فَصِيَامُ ثَلٰثَةِ اَيَّامٍ﴾ (Al-Māʾidah 5:89)
ثَالِثthālith: third. ﴿لَقَدْ كَفَرَ الَّذِيْنَ قَالُوْٓا اِنَّ اللّٰهَ ثَالِثُ ثَلٰثَةٍ﴾ (Al-Māʾidah 5:73)
ثُلَاثthulāth: three by three. ﴿مَثْنٰى وَثُلٰثَ وَرُبٰعَ﴾ (An-Nisāʾ 4:3)
ثُلُثthuluth: a third. ﴿فَلَهُنَّ ثُلُثَا مَا تَرَكَ﴾ (An-Nisāʾ 4:11)
ثَلَاثُوْنthalāthūn: thirty. ﴿وَوٰعَدْنَا مُوْسٰى ثَلٰثِيْنَ لَيْلَةً﴾ (Al-Aʿrāf 7:142)
Form II (tafʿīl) ثَلَّثَ يُثَلِّثُ تَثْلِيْثًاthallatha yuthallithu tathlīthan: to make three — hence the Christians' "tathlīth" (Trinity).