Tathatā, suchness or thusness, is the true nature of phenomena when seen without imposed concepts: not something behind things, but things as they are. The Mahāyāna uses it as a synonym for emptiness and for the dharmakāya. The Awakening of Faith speaks of the one mind and its suchness.
Suchness
Tathatā: things as they truly are, beyond conceptual distortion.
Also: tathata, thusness