The Qawaidul Ilal (قواعد الإعلال) book consists of two syllables, namely Qowaid and I'lal. Qowaid means rules and I'lal is a change in ilat letters (wawu, alif, yes). So in simple terms this book is a book that discusses Arabic grammar which aims to find out changes in the origin of a lafadz. In studying the science of shorof, it is not enough to only have capital by understanding the wazan fi'il. But one must also understand the rules of I'lal. As with the meaning of the name of the book itself, Qowaid is the plural form of Qoidah which means basic, reason, law. In Qowaidul I'lal there are 19 qoidah, so the name changed to the plural Qowaidul I'ilal which means rules in Arabic.