Buddha-nature or the seed of enlightenment. Buddha-nature or Buddha Principle refers to several related terms, most notably Tathāgatagarbha and Buddhadhātu. 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".