Kātyāyana (कात्यायन) also spelled as Katyayana (est. c. 6th to 3rd century BCE) was a Sanskrit grammarian, mathematician and Vedic priest who lived in ancient India. पतञ्जलीमहर्षिः Patanjali Maharshi said ecstatically:priyataddhitā dākṣiṇātyāḥ (प्रियतद्धिता दाक्षिणात्या: Meaning:Belonging to or living in south India.). This proves that he lived in the Southern India. Also Patanjali Maharshi also said 'yathā laukikavaidikēṣu ('यथा लौकिकवैदिकेषु'What does it mean?) which is looked upon as Katyayana's Vartikam. Katyayana has been linked to Vararuci by many although it is contested. He is considered the author of "Prakrita Prakasha" which is considered as the foundation of historical linguistics.