Tattva

Tattva (T. de nyid/de kho na nyid དེ་ཉིད་/དེ་ཁོ་ན་ཉིད་; C. shixiang 實相) is used in two senses:

1. ultimate reality, free from conceptual elaboration; a synonym of paramārtha
2. the central doctrine, or "principle," of a philosophical school; for example, as used in the title of texts such as the Tattvasamgraha and the Tattvasiddhi Śāstra.

The Princeton Dictionary states:

When contrasted with tathatā, tattva is the essential identity of a particular dharma, while tathatā is the common essential reality in which all dharmas partake.

Jan Willis states:

A literal rendering of tattva is "thatness" (tat = "that" and tva = "ness"), or "thusness," and refers to the true or actual state of things or affairs, i.e, their reality in themselves, apart from all adventitious elements and subjective biases. Etymologically, the term shares affinity with tathatā, which is generally translated "suchness" and which often appears as a synonym for śūnyatā, the true state of things, according to the Mahāyāna...

As a technical term, it is interesting that tattva is often used to delineate distinct and individual realities, especially in treatises associated with the yoga schools.

Further reading

• དེ་ཁོ་ན་ཉིད་, Christian-Steinert Dictionary
• de_kho_na_nyid, Rangjung Yeshe Wiki