(ن) شَكَرَ يَشْكُرُ شُكْرًا وَشُكْرَانًاshakara yashkuru shukran wa-shukrānan: to recognise someone's favour and acknowledge it, to give thanks; the lexicographers say that the original sense is of appearing and being filled (hence شَكِرَتِ النَّاقَةُshakirati an-nāqat = the she-camel's udders filled with milk), and thanks were given this name because in them the effect of the blessing becomes apparent. Its complement comes with the lām: شَكَرَ لَهُۥshakara lahu. ﴿لَئِنْ شَكَرْتُمْ لَاَزِيْدَنَّكُمْ﴾ (Ibrāhīm 14:7)
شَاكِرٌshākir (active participle, ism fāʿil): thankful, one who gives thanks. ﴿اِمَّا شَاكِرًا وَّاِمَّا كَفُوْرًا﴾ (Al-Insān 76:3)
شَكُوْرٌshakūr (فَعُوْلٌfaʿūl, intensive form (ṣīghat al-mubālaghah)): very thankful; and when used of Allah it means One who gives abundantly for a little deed. ﴿وَقَلِيْلٌ مِّنْ عِبَادِيَ الشَّكُوْرُ﴾ (Sabaʾ 34:13)
مَشْكُوْرٌmashkūr (passive participle, ism mafʿūl): one whose worth is appreciated.
Form V (tafaʿʿul) تَشَكَّرَ يَتَشَكَّرُ تَشَكُّرًاtashakkara yatashakkaru tashakkuran: to show gratitude in acknowledgement of a favour (this verb is not used in the Quran).