The word most frequently used in Aikido is ki. Ki is a very convenient word because it has both a deep meaning connected with nature and a light meaning which is used in daily life. It is very difficult to define ki and even more difficult to translate it into English. Therefore the word ki will be used in the explanation of Aikido.

In oriental thought, it is said that in the beginning there was chaos. The dust of chaos settled gradually to form the sun, the earth, the moon, and the stars. On the earth, the elements combined to become minerals, animal, and vegetable life. We call the chaotic conditions before the universe took shape ki. We say therefore that all things came from ki

Ki itself has neither beginning nor end, nor increase nor decrease. Though it shape was changed, ki itself was never changed. We can see many things around us all made from ki, and when they lose their shape, their elements return to ki. Depending on what you believe, you call it God, or Buddha, or Akua, or some other name.

Aikido is the way of at-one-ment with cosmic power or ki.

That is the deep meaning of ki.

What is the light meaning of ki used in our daily life? A good feeling, a bad feeling, a great feeling, timidity, vigor, courage, a retiring disposition, et cetera --- these are terms used in our daily life. In each word or phrase, the Japanese use ki as an integral part. The reason is that a human being was created from ki of the universe. While he receives ki, he is alive. Deprive him of ki and he dies; he loses his human shape. So long as his body is filled with ki and pours forth abundantly, he is vigorous and filled with courage. On the contrary, when his body has run out of ki, he is weak, cowardly, and retiring.

In Aikido training, we make every effort to learn to fill our body with ki and use it powerfully. Therefore, we must understand well the deep meaning of ki.

Koichi Tohei What is Aikido?, Rikugei Publishing House, Tokyo, 1962, page113