Bunkai:The term 'bunkai' refers to the taking apart or analysis of the techniques learned in a karate kata, as an application for self-defense. Bunkai is sometimes a set form of interpreting moves, usually governed by particular application of karate contained within kata. Techniques in a kata can have various interpretations applications, and levels of understanding, as can the bunkai which is to correspond to particular moves within a karate form.
The practice of bunkai, using applications for kata movement, may have been introduced to Okinawan Karate as early as the 1700's, and evolved in different ways. Techniques learned in the practice of bunkai include blocks, punches, grabs, kicks, throws, locks and others.
Practices in karate called 'kumai jutsu' or 'ippon kumite' (one point fighting) are used in learning bunkai and oyo. This seems to have a long tradition in Okinawan karate, thought to have been handed down from Ku Shanku, a Chinese Master. Bunkai has different levels of understanding. Various advanced, and complex techniques are practiced from interpretations of different kata, including weapons. Bunkai can be practiced with a partner, or alone.
Oyo: Oyo is a term meaning application or putting to a particular use (Kodansha's Furigana Japanese Dictionary, 1999) Oyo, like bunkai is another term used to qualify moves garnered from kata, but this refers to another level of interpretation which does not always correlate with specific or generally known applications of a kata technique. Oyo can be techniques implicated according to a given condition.
Oyo, is best practiced with partners. There are levels of oyo like there are levels of bunkai. Oyo can range from the simple execution of karate application, to applying complex theories of kata, not necessarily related to particular moves within kata. Oyo stresses utility, while bunkai stresses analysis.
At the Broken Bokken Dojo, we incorporate both Bunkai and Oyo to our Kata, especially Sanchin Kata. Sanchin is so 'simple' in movement I like to think of it as a Universal Kata. As we study Kusanku Kata and Sanchin throughout the winter months we will analyze Bunkai and Oyo and point out the difference.