 The " is the central part of 's grammar, and by far the most complex.The "Ashtadhyayi" is the oldest linguistic and grammar text of Sanskrit surviving in its entirety, and Pāṇini refers to older texts and authors such as the "Unadisutra", "Dhatupatha", and "Ganapatha" some of which have only survived in part.It complements the Vedic ancillary sciences such as the "Niruktas", "Nighantus", and "Shiksha".