interpretation / exegesis / explanation
Form II maṣdar (تَفْعِيل). Verb: فَسَّرَ (to explain/interpret). The academic discipline of Quranic interpretation is called ʿilm at-tafsīr.
Tafsīr is one of the most important Islamic sciences. Famous works include Tafsīr aṭ-Ṭabarī, Tafsīr Ibn Kathīr, and Tafsīr al-Jalālayn.