Definition of "Mahajanapada"

We know that there were sixteen mahajanapadas in the 6th and 5th centuries BCE but there were more than one hundred janapadas, some of which were independent and some others were included in the bigger mahajanapadas.

2006, Irā Kiruṣṇamūrtti, Irāmaccantiran̲ Nākacāmi, Sangam: numismatics and cultural history : essays in honour of Dr. R. Krishnamurthy‎, New Era Publications, pages 66–67

Among the 16 mahajanapadas the monarchical states of Kosala, Vatsa, Avanti, and Magadha, along with the non‐monarchical mahajanapada of the Vrijis or Vajjis, attained political prominence by eclipsing other contemporary powers. However, it was the mahajanapada of Magadha which ultimately rose to prominence.

2016 January 11, Susmita Basu Majumdar, “Magadha, Kingdom of”, in N. Dalziel, J. M. MacKenzie, editors, The Encyclopedia of Empire‎, Wiley

Pataliputra was founded by Udayin while Rajgriha was founded by Bimbisar. Vajji was the ancient name of north Bihar. The territory of the Vajji Mahajanapada was located on the north of the Ganges river and extended up to the Terai region of Nepal.

2019 April 1, 2200+ MCQs with Explanatory Notes For HISTORY 2nd Edition‎, 2nd edition, New Delhi: Disha, page A23