Ken has 3 characteristic called "Sho" (Pine), "Chiku," (Bamboo) and "Bai" (Plum). These characteristics are independent of each other and yet are linked up together to produce variations, the basic form of which is kumi-tachi (matching exercise). All of the Ken techniques are adaptable to Taijutsu (empty-handed exercises) adding depth to the dimensions of Aikido.
Traditional Aikido, Vol 5, p. 22