(ض) كَذَبَ يَكْذِبُ كَذِبًا وَكِذْبًاkadhaba yakdhibu kadhiban wa-kidhban: to lie, to report contrary to fact. ﴿وَلَهُمْ عَذَابٌ اَلِيْمٌۢ بِمَا كَانُوْا يَكْذِبُوْنَ﴾ (Al-Baqarah 2:10)
كَذِبٌkadhib (verbal noun, maṣdar, also used as an adjective): a lie; false. ﴿وَجَآءُوْ عَلٰى قَمِيْصِهِۦ بِدَمٍ كَذِبٍ﴾ (Yūsuf 12:18)
كَاذِبٌkādhib pl. كٰذِبُوْنَkādhibūna, feminine كَاذِبَةٌkādhibah (active participle, ism fāʿil): a liar. ﴿نَاصِيَةٍ كَاذِبَةٍ خَاطِئَةٍ﴾ (Al-ʿAlaq 96:16)
كَذَّابٌkadhdhāb (intensive form on the pattern of فَعَّالٌfaʿʿāl): a great liar. ﴿سَيَعْلَمُوْنَ غَدًا مَّنِ الْكَذَّابُ الْاَشِرُ﴾ (Al-Qamar 54:26)
Form II (tafʿīl) كَذَّبَ يُكَذِّبُ تَكْذِيْبًا وَكِذَّابًاkadhdhaba yukadhdhibu takdhīban wa-kidhdhāban: to deny someone or something, to declare false. ﴿فَبِاَيِّ اٰلَآءِ رَبِّكُمَا تُكَذِّبٰنِ﴾ (Ar-Raḥmān 55:13); ﴿وَكَذَّبُوْا بِاٰيٰتِنَا كِذَّابًا﴾ (An-Nabaʾ 78:28); مُكَذِّبٌmukadhdhib pl. مُكَذِّبِيْنَmukadhdhibīna (active participle, ism fāʿil): a denier. ﴿وَيْلٌ يَّوْمَئِذٍ لِّلْمُكَذِّبِيْنَ﴾ (Al-Mursalāt 77:15)