Apāṇinīya vyākaraṇa (non-Pāṇinian grammar) refers to the various Sanskrit grammatical traditions based on root texts other than Pāṇini’s Aṣṭādhyāyī. The extant non-Pāṇinian grammars are all post-Pāṇinian, and all stemming from the common era. A large number, if not all, of these grammars are modelled on the Aṣṭādhyāyī with innovations in mostly limited to terminology and arrangement of material. Some prominent non-Pāṇinian grammatical schools are the Kātantra, the Cāndra, the Jainendra, the Śākaṭāyana, and the Sārasvata. Śarvavarman’s Kātantrasūtra (possibly c. 50 AD) and Candragomin's Candrasūtra (c. 450 AD) are among the most influential non-Pāṇinian grammars. The Kātantrasūtra is a pedagogical and practical grammar for Sanskrit learners at the level of beginners; the Candrasūtra is a modified and updated version of the Aṣṭādhyāyī.