The meaning of ku, which is a part of the Buddhist concept of Three Truths (Ke, Ku and Chu)
Ke/temporary existence- Can be thought of as life's manifestations and earthly phenomena.
Ku is that which can not be perceived with the senses but exists as pure potential. Non substantiality. Ku is used to describe the state we are in after we die. "Ku is entirely different from non-existence. It is the potential-void combining the three views of existence: Ketai, Kutai and Chutai."
Chu/The Middle Way The way which both transcends and unites dualities such as life and death.The realization of the unchanging essence of the universe. This concept is so difficult to grasp, it has been explained by saying what it is not; in the Eightfold Negations: 'neither birth nor death, neither cessation nor permanence, neither identity nor difference, neither coming nor going.'
Ideas (ku) become realized as tangible changes or actions (ke). The nature (ku) of these actions will be influenced by Chu. Chu is the permeating life force of the universe; it may be compared to our essence, which in turn is shaped by our dominant life state.
The concepept of ku, has been translated as latency, non-substantiality, emptiness and void. The first articulations of this idea comes from Nagarjuna. He believed that the state of "neither existence nor nonexistence" described in this concept expressed the true nature of all things. The paradoxical nature of this idea, however, makes it somewhat foreign to Western dualist logic. Ku, however, is down-to-earth, and in fact consistent with the findings of contemporary science.
Modern physics, in attempting to discover the essence of matter, has arrived at a description of the world that is very close to that of Nagarjuna. What scientists have discovered is that there is no actual, easily identifiable "thing" at the basis of matter. Subatomic particles, the building blocks of the physical world that we inhabit, appear to oscillate between states of being and nonbeing. Instead of a fixed "thing" in a particular place, we find only shifting waves of probability. At this level, the world is actually a highly fluid and unpredictable place, essentially without substance. It is this non-substantial nature of reality that the concept of ku describes.