(ن) كَفَرَ يَكْفُرُ كُفْرًا وَكُفُوْرًا وَكُفْرَانًاkafara yakfuru kufran wa-kufūran wa-kufrānan: the original meaning is to cover a thing, to hide it; then (1) to hide a favour, i.e. to be ungrateful (2) to hide the truth, i.e. to refuse to believe. ﴿اِنَّ الَّذِيْنَ كَفَرُوْا سَوَآءٌ عَلَيْهِمْ﴾ (Al-Baqarah 2:6); ﴿وَاشْكُرُوْا لِيْ وَلَا تَكْفُرُوْنِ﴾ (Al-Baqarah 2:152)
كَافِرٌkāfir pl. كٰفِرُوْنَ وَكُفَّارٌ وَكَفَرَةٌkāfirūna wa-kuffār wa-kafarah, feminine كَافِرَةٌkāfirah pl. كَوَافِرُkawāfiru (active participle, ism fāʿil): (1) a denier, an ingrate (2) a farmer (one who hides the seed in the soil). ﴿قُلْ يٰٓاَيُّهَا الْكٰفِرُوْنَ﴾ (Al-Kāfirūn 109:1); ﴿كَمَثَلِ غَيْثٍ اَعْجَبَ الْكُفَّارَ نَبَاتُهُۥ﴾ (Al-Ḥadīd 57:20)
كَفُوْرٌkafūr (intensive form on the pattern of فَعُوْلٌfaʿūl) and كَفَّارٌkaffār (intensive form on the pattern of فَعَّالٌfaʿʿāl): utterly ungrateful, an obstinate denier. ﴿اِنَّ الْاِنْسَانَ لَكَفُوْرٌ﴾ (Al-Ḥajj 22:66)
Form II (tafʿīl) كَفَّرَ يُكَفِّرُ تَكْفِيْرًاkaffara yukaffiru takfīran: to cover over and efface (an evil or its punishment), to remove. ﴿رَبَّنَا فَاغْفِرْ لَنَا ذُنُوْبَنَا وَكَفِّرْ عَنَّا سَيِّاٰتِنَا﴾ (Āl ʿImrān 3:193); كَفَّارَةٌkaffārah (noun, ism dhāt): that which is paid to make amends for a fault, an expiation. ﴿فَكَفَّارَتُهُۥٓ اِطْعَامُ عَشَرَةِ مَسٰكِيْنَ﴾ (Al-Māʾidah 5:89)