Everyone who’s been training in karate for more than a week or two knows that the kiai is a loud yell. That would seem to be pretty simple. But in reality the subject of the kiai is complex and profound, involving critical aspects of the body, the mind, and the spirit, and having numerous uses and applications. In truth, no one masters or even understands a martial art without mastering the kiai. So it is important that students realize from the very start that “the yell” is not a trivial, expendable, slightly silly bit of melodrama; rather, it is a core concept and an essential skill to be taken very seriously and to be practiced and refined at every opportunity.
Derivation
As the word implies, a central aspect of kiai is ki, originating in the Chinese word qi, in reference to breath, emotions, and (in Oriental medical theory) life energy force. Martial artists in the Orient have long believed they can harness this energy through correct training and use it to achieve paranormal fighting abilities. One method of channeling ki energy is the kiai…
The term kiai is a contracted nominal form of the phrase ki ga au (literally, to harmonize), which in the martial arts means to channel your own energy in harmony with that of your opponent so as to increase the destructive force of your technique. A related phrase is ki o awaseru, to blend or harmonize with another’s intent or action. This is a high-level concept in fighting, to “become one” with your opponent rather than clashing ineffectually, and it is interesting to find it embodied in a word which seemingly refers to a yell. This accounts for the common but perplexing translation of kiai as “spirit meeting”. In tactical terms it means that the stronger mind fuses with the weaker in order to control it. For the samurai this was an aspect of shinki-jutsu, the general art of uniting opposing minds under the control of one. In an even broader interpretation, kiai is sometimes regarded as the manifestation of the Active Principle (Aiki or God) of the Universe.
In the sense of its harmonizing effect, kiai also bridges the mind and body of the practitioner himself to achieve a perfect meeting and coordination of the timing and focus of a technique at the moment of execution…
The kiai is so fundamental to karate training that instructors commonly use it as one measure of a student’s progress. Donn Draeger, in his 1973 book on Classical Budo, wrote:
`A well-made kiai produces a characteristic sound that makes the ears ring: it seems to come from a source deep within the trainee, and not merely to be caused by the vibration of his vocal cords. The tonal fidelity of the kiai is much like the unforgettable, deep-seated rumble of a lion at bay. The kiai indicates the degree of integration of mind and body in the execution of a technique. It is an unfailing source of information for the master, who thereby knows the trainee’s level of achievement…’
Master Hidy Ochiai remarks that volume is not always a requirement for a good fighting kiai: “When you are at an advanced level you can execute a good kiai without obvious shouting or yelling. Mere shouting does not mean a good kiai, and a good kiai may or may not produce a loud shouting or yelling…” Kiai is essential for students, but ultimately, as Ocahiai says, the actual vocalization of a sound becomes optional at the master level. Sun Tsu, in the ancient Chinese classic The Art of War, wrote that in swordsmanship the acme is reached when “at last practice is silent”.

