空 Kū or sora, most often translated as "Void", but also meaning "sky" or "Heaven", represents those things beyond our everyday experience, particularly those things composed of pure energy. Bodily, kū represents spirit, thought, and creative energy. It represents our ability to think and to communicate, as well as our creativity. It can also be associated with power, creativity, spontaneity, and inventiveness.
Kū is of particular importance as the highest of the elements. In martial arts, particularly in fictional tales where the fighting discipline is blended with magic or the occult, one often invokes the power of the Void to connect to the quintessential creative energy of the world. A warrior properly attuned to the Void can sense his surrounding and act without thinking, and without using his physical senses.