ADI:

The Adi tribe is the biggest tribe of Arunachal Pradesh. It comprises of several sub tribes. The Adi area is situated in the central region of Arunachal Pradesh., in the east and west Siang districts. The word Adi in the tribal language means people living in the hills, and this is preffered  by the tribe instead of being called Abores, which is the old name of the tribe. The Adis thus are the tribes living in the hills beyond Sila-Pathar and Jonai of Assam valley on the north bank of the Brahmaputra. Their area is traversed by hill ranges covered with dense forests. They populate the valleys of Siang river right from its extreme point from Gelling to the foothill at Pasighat from where it enters Assam valley.

Source: H.M. Bareh. “Encyclopedia of North-East India” Mittal Publications. New Delhi.