Buddha-nature or Buddha Principle refers to several related terms, most notably tathāgatagarbha and buddhadhātu.[note 2] Tathāgatagarbha means "the womb" or "embryo" (garbha) of the "thus-gone" (tathagata), or "containing a tathagata", while buddhadhātu literally means "Buddha-realm" or "Buddha-substrate". The terms refer to the notion that the luminous mind of the Buddhas is inherently present in every sentient being, and will shine forth when it is cleansed of the defilements, c.q. when the nature of mind is recognised for what it is.
The term tathāgatagarbha may mean "embryonic tathāgata", "womb of the tathāgata", or "containing a tathagata". Various meanings may all be brought into mind when the term tathagatagarbha is being used.
The Sanskrit term tathāgatagarbha is a compound of two terms, tathāgata and garbha:
tathāgata means "the one thus gone", referring to the Buddha. It is composed of "tathā" and "āgata", "thus come", or "tathā" and "gata", "thus gone". The term refers to a Buddha, who has "thus gone" from samsara into nirvana, and "thus come" from nirvana into samsara to work for the salvation of all sentient beings. garbha, "womb", "embryo", "center", "essence".
The term "Buddha-nature" (traditional Chinese: 佛性; ; pinyin: fóxìng, Japanese: busshō) is closely related in meaning to the term tathāgatagarbha, but is not a translation of this term. it refers to that what is essential in the human being.
The corresponding Sanskrit term is buddhadhātu. It has two meanings, namely the nature of the Buddha, equivalent to the term dharmakāya, and the cause of the Buddha The link between the cause and the result is the nature (dhātu) which is common to both, namely the dharmadhātu.
Matsumoto Shirō also points out that "Buddha-nature" translates the Sanskrit-term buddhadhātu, a "place to put something," a "foundation," a "locus." According to Shirō, it does not mean "original nature" or "essence," nor does it mean the "possibility of the attainment of Buddhahood," "the original nature of the Buddha," or "the essence of the Buddha."
In the Vajrayana, the term for Buddha-nature is sugatagarbha.