ص و مṣ-w-m
(ن) صَامَ يَصُوْمُ صَوْمًا وَصِيَامًاṣāma yaṣūmu ṣawman wa-ṣiyāman (original form: صَوَمَṣawama): to stop, to abstain; in Arabic it is also said of a horse refusing its fodder and of the sun standing still at high noon.
شرعًاshrʿan: abstaining from food, drink and sexual desire.
صَائِمṣāʾim pl. صَائِمُوْن وَصَائِمَاتṣāʾimūn wa-ṣāʾimāt (active participle, ism fāʿil). A Quranic point: the fast of Maryam (peace be upon her) was an abstention from speech — ﴿إِنِّيْ نَذَرْتُ لِلرَّحْمٰنِ صَوْمًا فَلَنْ أُكَلِّمَ الْيَوْمَ إِنْسِيًّا﴾ (Maryam 19:26), which is the clearest proof of the original meaning of the root. 14 times in the Quran.