(ن) شَدَّ يَشُدُّ شَدًّا وَشِدَّةًshadda yashuddu shaddan wa-shiddatan: to be or make firm, heavy or strong; it is then used both intransitively and transitively (without a preposition and also with certain prepositions) in various meanings: (1) to be firm or heavy, as in شَدَّ الشَّيْءُshadda ash-shayʾ (the thing became firm) (2) to tie a knot tightly, as in شَدَّ الْعُقْدَةَshadda al-ʿuqdata (he tied the knot tightly) (3) to help someone or give him strength, as in شَدَّ عَضُدَهُۥshadda ʿaḍudahu (he strengthened his arm) and شَدَّ اَزْرَهُۥshadda azrahu (he strengthened his back or his power). ﴿سَنَشُدُّ عَضُدَكَ بِاَخِيْكَ﴾ (Al-Qaṣaṣ 28:35) (4) to prepare for a journey, as in شَدَّ رِحَالَهُۥshadda riḥālahu; in this case it takes the preposition «عَلٰىʿalā».
اَشُدٌّashudd (noun, ism dhāt): firmness, severity; «بَلَغَ اَشُدَّهُۥbalagha ashuddahu» i.e. he reached the age of maturity and full strength. ﴿حَتّٰٓى اِذَا بَلَغَ اَشُدَّهُۥ﴾ (Al-Aḥqāf 46:15)
شَدِيْدٌshadīd pl. اَشِدَّاءُ وَشِدَادٌashiddāʾu wa-shidād (adjective on the pattern of فَعِيْلٌfaʿīl): always and in every state severe, hard. ﴿اِنَّ اللّٰهَ شَدِيْدُ الْعِقَابِ﴾ (Al-Baqarah 2:196); ﴿اَشِدَّآءُ عَلَي الْكُفَّارِ﴾ (Al-Fatḥ 48:29); ﴿سَبْعًا شِدَادًا﴾ (An-Nabaʾ 78:12)
Form V (tafaʿʿul) تَشَدَّدَ يَتَشَدَّدُ تَشَدُّدًاtashaddada yatashaddadu tashaddudan: to act with severity; to be strict (this verb is not used in the Quran).
Form VIII (iftiʿāl) اِشْتَدَّ يَشْتَدُّ اِشْتِدَادًاishtadda yashtaddu ishtidādan: to become firm, to become hard. ﴿كَرَمَادِ ۨاشْتَدَّتْ بِهِ الرِّيْحُ﴾ (Ibrāhīm 14:18)