(ض، ک) وَحَدَ يَحِدُ وَحْدًا وَوَحُدَ يَوْحُدُ وَحَادَةًwaḥada yaḥidu wa-ḥdan wa-waḥuda yawḥudu wa-ḥādatan: to be alone and unique, to be singular. (This verb is not used in the Quran.)
وَاحِدٌwāḥid, feminine وَاحِدَةٌwāḥidah (active participle, ism fāʿil): one, alone. ﴿وَاِلٰهُكُمْ اِلٰهٌ وَّاحِدٌ﴾ (Al-Baqarah 2:163)
اَحَدٌaḥad (اصلاً وَحَدٌaṣlan wa-ḥad, the wāw changed to hamzah): one, unique; of God: He who has no second. ﴿قُلْ هُوَ اللّٰهُ اَحَدٌ﴾ (Al-Ikhlāṣ 112:1)
وَحِيْدٌwaḥīd (adjective on the pattern of فَعِيْلٌfaʿīl): alone, solitary. Only once in the Quran: ﴿ذَرْنِيْ وَمَنْ خَلَقْتُ وَحِيْدًا﴾ (Al-Muddaththir 74:11)
وَحْدَهُۥwaḥdahu (verbal noun (maṣdar) as circumstantial accusative (ḥāl)): alone, by oneself. ﴿وَاِذَا ذُكِرَ اللّٰهُ وَحْدَهُ اشْمَاَزَّتْ قُلُوْبُ الَّذِيْنَ لَا يُؤْمِنُوْنَ بِالْاٰخِرَةِ﴾ (Az-Zumar 39:45)
Form II (tafʿīl) وَحَّدَ يُوَحِّدُ تَوْحِيْدًاwaḥḥada yuwaḥḥidu tawḥīdan: to make one; to affirm as one; to declare unique (this verb is not used in the Quran).
Form VIII (iftiʿāl) اِتَّحَدَ يَتَّحِدُ اِتِّحَادًاittaḥada yattaḥidu ittiḥādan: (of several things) to unite into one; to be combined (this verb is not used in the Quran).