prAtiSAKyaM A grammatical treatise laying down rules for the phonetic changes which words in any Śākhā of the Vedas undergo, and teaching the mode of pronouncing the accents &c. (There exist four Prātiśākhyas, one for the Śākala branch of Ṛgveda, one for each of the two branches of the Yajurveda, and one for the Atharvaveda).