The (Devanagari अष्टाध्यायी) is a grammar that describes a form of an early Indo-Aryan language: Sanskrit. Authored by Sanskrit philologist and scholar Pāṇini and dated to around 500 BCE, it describes the language as current in his time, specifically the dialect and register of an élite of model speakers, referred to by Pāṇini himself as śiṣṭa. The work also accounts both for some features specific to the older Vedic form of the language, as well as certain dialectal features current in the author's time. The Aṣṭādhyāyī employs a derivational system to describe the language, where real speech is derived from posited abstract utterances formed by means of affixes added to bases under certain conditions. The Aṣṭādhyāyī is supplemented by three ancillary texts: akṣarasamāmnāya, dhātupāṭha and gaṇapāṭha. Etymology Aṣṭādhyāyī is made of two words aṣṭa-, 'eight' and adhyāya-, 'chapter', thus meaning eight-chaptered, or 'the book of eight chapters'. Background Grammatical tradition By 1000 BCE, a large body of hymns composed in the oldest attested form of the Proto-Indo-Aryan language had been consolidated into the Rigveda, which formed the canonical basis of the Vedic religion, being transmitted from generation to generation entirely orally. In the course of the following centuries, as the popular speech evolved, growing concern among the guardians of the Vedic religion that the hymns be passed on without 'corruption' led to the rise of a vigorous, sophisticated grammatical tradition involving the study of linguistic analysis, in particular phonetics alongside grammar. The high point of this centuries-long endeavour was Pāṇini's Aṣṭādhyāyī, which eclipsed all others before him. While not the first, the Aṣṭādhyāyī is the oldest linguistic and grammar text, and one of the oldest Sanskrit texts, surviving in its entirety. Pāṇini refers to older texts such as the Unādisūtra, Dhātupāṭha, and Gaṇapātha but some of these have only survived in part. Arrangement The Aṣṭādhyāyī consists of 3,959 sūtras in eight chapters, which are each subdivided into four sections or pādas. There are different types of sūtras, with the vidhisūtra - operational rules, being the main one. The other, ancillary sūtras, are: paribhāṣā - metarules adhikāra - headings atideśa·sūtra - extension rules niyama·sūtra - restrictive rules pratiṣedha- & niṣedha·sūtra - negation rules Related fields The Aṣṭādhyāyī is the foundation of Vyākaraṇa, one of the Vedic ancillary fields (Vedāṅgas), and complements others such as the Niruktas, Nighaṇṭus, and Śikṣā. Regarded as extremely compact without sacrificing completeness, it would become the model