Prajñāpāramitā - A class of Mahāyāna sūtras which represents some of the earliest known literature of this genre of Buddhism. There are around forty texts associated with this category, though the most widespread is the exceedingly brief Prajñāpāramitāhṛdayasūtra, popularly known as the Heart Sūtra. This class of literature is typically associated with the second turning of the dharma wheel and especially with the teachings on emptiness (śūnyatā). As such, these texts were the primary scriptural source for the philosophy of the Madhyamaka school. Skt. प्रज्ञापारमिता Tib. ཤེས་རབ་ཀྱི་ཕ་རོལ་ཏུ་ཕྱིན་པ་,ཤེར་ཕྱིན་ Ch. 般若波羅蜜多