You no doubt have seen sentences such as the following:أكرمني إكراما عظيما . This is usually referred to as the cognate accusative in English. It is generated by inserting the verbal noun of the verb in the sentence which is usually then modified by an adjective. The verbal noun is most often indefinite and accusative. The Arabic sentence above literally means “He honored me a great honoring. Normally it would be translated “He honored me greatly.”
We want to say “He studied Arabic for a long time,” and use the cognate accusative in order to do so. The verb we will use is درس of course. “He studied Arabic” is درس اللغة العربية Now we will add the verbal noun of درس to the sentence. The verbal noun of درس is دراسة We will place دراسة at the end of the sentence. It will be indefinite and accusative. So now we have درس اللغة العربية دراسة Now we add طويلة to the sentence. It will completely agree with ” دراسة. So now we have:
دَرَسَ اللغةَ العربيةَ دراسةً طويلة.ً
This use of the verbal noun is quite common. It also has some variations. Sometimes the verbal noun is not modified. Thus you could have أكرمني إكراماً. Here the verbal noun adds some emphasis, but not much.
Sometimes the verbal noun is put into an idaafa as in كانوا يعبدون الله عبادة الثنيين “They used to worship God like idolaters (the worship of idolaters).”
There are other uses of the verbal noun along the these lines. They will be easy to spot when you come to them.