Tiantai, also known as the Tendai school of Buddhism, is a Mahayana Buddhist tradition that originated in China in the 6th century. It is known for its unique approach to the concept of emptiness, which is a central teaching in Buddhism. Emptiness, or shunyata in Sanskrit, refers to the idea that all phenomena lack inherent existence and are instead dependent on causes and conditions.

In Tiantai, the concept of emptiness is closely linked to the teachings of the Lotus Sutra, which is considered the ultimate and most comprehensive teaching of the Buddha. Tiantai holds that all Buddhist teachings, including the concept of emptiness, are integrated and unified within the Lotus Sutra. This means that emptiness is not seen as a separate or independent teaching, but rather as an essential aspect of the Lotus Sutra.

Tiantai also emphasizes the concept of the "Middle Way," which is the idea that all phenomena exist in a state of neither absolute existence nor absolute non-existence. This middle way approach to emptiness is seen as a way to avoid falling into extreme views or clinging to fixed concepts.

In Tiantai, emptiness is not seen as a negation of existence, but rather as a way to understand the true nature of reality. The Lotus Sutra teaches that all phenomena are ultimately empty of inherent existence, but at the same time, they also possess an ultimate reality or "Suchness" (tathata). This Suchness is beyond conceptualization and is the true nature of all things.

Tiantai also emphasizes the concept of the "three truths," which are the provisional truth, the relative truth, and the ultimate truth. The provisional truth refers to the conventional understanding of reality, while the relative truth refers to the interdependent nature of all phenomena. The ultimate truth, on the other hand, refers to the true nature of reality, which is emptiness.

According to Tiantai, all three truths are interconnected and must be understood together in order to have a complete understanding of emptiness. The Lotus Sutra teaches that all beings have the potential to attain Buddhahood and realize the ultimate truth of emptiness.

In summary, Tiantai's approach to emptiness is closely tied to the teachings of the Lotus Sutra and emphasizes the Middle Way, the three truths, and the concept of Suchness. Emptiness is seen as an essential aspect of the ultimate truth and is not separate from other Buddhist teachings. By understanding emptiness, one can gain a deeper understanding of the true nature of reality and ultimately attain enlightenment.