(س) مَرِضَ يَمْرَضُ مَرَضًاmariḍa yamraḍu maraḍan: to be ill; the basic sense is departing from balance and growing weak, which is why the word is used not only of the body but also of corruption in the heart, in intention and in affairs. ﴿وَاِذَا مَرِضْتُ فَهُوَ يَشْفِيْنِ﴾ (Ash-Shuʿarāʾ 26:80)
مَرَضٌmaraḍ (verbal noun, maṣdar; also a noun, ism dhāt): illness; in the Quran mostly of the disease of the heart (hypocrisy and doubt). ﴿فِيْ قُلُوْبِهِمْ مَّرَضٌ فَزَادَهُمُ اللّٰهُ مَرَضًا﴾ (Al-Baqarah 2:10)
مَرِيْضٌmarīḍ pl. مَرْضٰىmarḍā (adjective on the pattern of فَعِيْلٌfaʿīl): sick; the plural of this pattern comes on فَعْلٰىfaʿlā, as قَتِيْلٌqatīl ← قَتْلٰىqatlā, because this pattern is specific to affliction. ﴿فَمَنْ كَانَ مِنْكُمْ مَّرِيْضًا اَوْ عَلٰى سَفَرٍ﴾ (Al-Baqarah 2:184); ﴿عَلِمَ اَنْ سَيَكُوْنُ مِنْكُمْ مَّرْضٰى﴾ (Al-Muzzammil 73:20)