Adat (Arabic ﻋﺎﺪﺔ ) is a set of local and traditional laws and dispute resolution systems in many parts of Nusantara. In older Malay language, adat refers to the customary laws, the unwritten traditional code regulating social, political, and economical as well maritime laws.
Two kinds of Malay adat laws were developed before the 15th century:
One of the most important scholars of Adat Law was Cornelis van Vollenhoven.