Tattva (Sanskrit, (that-ness”)
In Buddhism tattva does not carry the same technical philosophical connotation as in other Eastern religions. The proto-Mahayanist Prajnaptivadins defined tattva as the real phenomenon that underlies concept (prajnapti). In the Vijhnanavada (Yogacara) this meaning is substantially retained, though now extended to include the totality of entities.
The Ratnagotravibhaga of Asanga talks of reality (tattva) being devoid of subject-object dichotomy, and other texts by the same author state that since words and concepts do not partake of the nature of things they denote, tattva is ultimately inexpressible.
Authors representing the Madhyamaka tendency are careful not to use tattva in the Yogacarin sense in their effort to avoid all term that may be taken as absolutes. Nagarjuna does, however, talk of the reality or truth (tattva) of the Buddha’s teaching.
In Jainism, tattva is the categorical (true or genuine) constituent of appearance and release. “Tattva (the categories of truth) are sentient selves (jiva), non-sentient selves, inflow of karmic particles into the self, binding of the karmic particles to the self, blocking its inflow, shedding it, liberation (moksa)” (Tattvartha[dhigama]-Sutra 1. 4)
Bowker, John, The Oxford Dictionary of World Religions, New York, Oxford University Press, 1997, pp. 956-957