Arabic verbs are organized into ten main forms (أوزان), each adding a specific shade of meaning to the root concept. Understanding these forms is essential for Quranic comprehension, as the Quran uses all ten forms extensively, and recognizing a verb's form often reveals its meaning even without a dictionary.
Form I (فَعَلَ) is the base form and by far the most common. It carries the basic meaning of the root: كَتَبَ (to write), عَلِمَ (to know), ذَهَبَ (to go). Form II (فَعَّلَ) often intensifies the meaning or makes it transitive: عَلَّمَ (to teach — causing someone to know), كَسَّرَ (to shatter — intensive breaking). Form III (فَاعَلَ) often implies doing something with someone: قَاتَلَ (to fight with someone), جَاهَدَ (to strive/struggle against).
Form IV (أَفْعَلَ) often makes intransitive verbs transitive: أَسْلَمَ (to submit/become Muslim — from سَلِمَ, to be safe), أَنزَلَ (to send down — from نَزَلَ, to descend). Form V (تَفَعَّلَ) is often the reflexive of Form II: تَعَلَّمَ (to learn — reflexive of عَلَّمَ, to teach). Form VI (تَفَاعَلَ) implies mutual or pretended action: تَعَاوَنَ (to cooperate with each other).
Form VII (اِنْفَعَلَ) is often passive: اِنْكَسَرَ (to break, intransitive). Form VIII (اِفْتَعَلَ) is often reflexive: اِجْتَمَعَ (to gather, intransitive). Form IX (اِفْعَلَّ) is rare and relates to colors and defects: اِحْمَرَّ (to become red). Form X (اِسْتَفْعَلَ) often means to seek or consider: اِسْتَغْفَرَ (to seek forgiveness), اِسْتَكْبَرَ (to consider oneself great/to be arrogant).
In the Quran, being able to identify a verb's form immediately tells you something about its meaning, even if you've never seen that specific verb before. This is one of the most powerful tools Sarf gives you for Quranic understanding, and it's drilled extensively through Ilm Al Lughah's Sarf courses and verb conjugation flashcards.