Buddhadhātu / Buddha-nature
Buddha-nature is a latent seed or potentiality inherent to the sentient beings that may, once matured, result in the achievement of buddhahood. Buddhanature, or buddha element, is universally present in all sentient beings, thanks to which, those who can withstand the difficult engagement of (Buddhist) practice throughout their lives in samsara, will finally attain the goal of enlightenment. Conceptually, it has a close affinity with another term tathāgatagarbha (literally the womb of the Tathāgata), which emphasizes the nature of purity as being innate in the minds of all sentient beings and capable of being manifested under proper circumstances.
I have often proclaimed the universality of the buddha-nature in all sentient beings, including icchantikas (literally one who is subject to great desire, hence according to certain schools should be bereft of all the possibilities to achieve buddhahood). Icchantikas, though devoid of any meritorious deeds accumulated so far throughout their past lives, still possess the buddha-nature and thus will be able to engage in the wholesome activities in the future. (Great Discourse on the Final Nirvana)