The language of the Quran is classical and there are words which are not used today. Gathered in this wonderful book is a list of unfamiliar vocabulary with the meaning (in modern standard Arabic), organised by Surah. This is useful if you’re looking to memorise keywords of the Quran.

As-Siraaj fii Bayaan Gharib al-Qur’an / السراج في بيان غريب في القرآن