Definition: name of an ancient school of grammar and of the treatise also, belonging to that school, believed to have been written under instructions of Indra. The work is not available. Patañjali mentions that Bṛhaspati instructed Indra for one thousand celestial years and still did not finish his instructions in words': (M. Bh. I.1.1). The Taittirīya Saṁhitā mentions the same. Pāṇini has referred to some ancient grammarians of the East by the word प्राचाम् without mentioning their names, and scholars like Burnell think that the grammar assigned to Indra is to be referred to by the word प्राचाम्. The Bṛhatkathāmañjarī remarks that Pāṇini's grammar threw into the background the Aindra Grammar. Some scholars believe that Kalāpa grammar which is available today is based upon Aindra,just as Cāndra is based upon Pāṇini's grammar. References to Aindra Grammar are found in the commentary on the Sārasvata Vyākaraṇa, in the Kavikalpadruma of Bopadeva as also in the commentary upon the Mahābhārata by Devabodha.Quotations, although very few, are given by some writers from the work. All these facts prove that there was an ancient pre-Pāṇinian treatise on Grammar assigned to इन्द्र which was called Aindra-Vyākaraṇa.For details see Dr.Burnell's 'Aindra School of Sanskrit Grammarians' as also Vol. VII pages 124-126 of Vyākaraṇa Mahābhāṣya, edited by the D.E.Society, Poona.