س ت تs-t-t
— سِتَّةٌsittah / سِتٌّsitt: the number six. The original form was سِدْسٌsids (which is why a sixth is called سُدُسٌsudus and the plural is اَسْدَاسٌasdās); the dāl was changed to tāʾ and assimilated: سِدْتٌsidt ⟵ سِتٌّsitt; this morphological point is particularly noteworthy: the root of the number is s-d-s, but the word took the shape s-t-t. ﴿خَلَقَ السَّمٰوٰتِ وَالْاَرْضَ فِيْ سِتَّةِ اَيَّامٍ﴾ (Al-Aʿrāf 7:54)
سِتُّوْنَsittūna: sixty. ﴿فَاِطْعَامُ سِتِّيْنَ مِسْكِيْنًا﴾ (Al-Mujādilah 58:4)This root occurs 8 times in the Quran.