Re- Title of this thread:
Bunkai is a Japanese word that means taking apart, dismantling, or breaking down into components (Kodansha, 1999). Therefore, in karate the term kata bunkai would imply that one is taking the kata and breaking it down in to more manageable parts. This is often done with areas of a kata that are more challenging to the students than other parts. Rather than terming this type of activity as the study of kata application, it is perhaps more accurate to label it as kata analysis.
The second term, oyo, may be translated as application or putting to a particular use (Kodansha, 1999). Therefore, if kata can be defined as a prescribed sequence of techniques against imaginary opponents, one manner in which oyo be defined is simply as kata with real opponents. In other words, oyo is the interpretation, application and demonstration of the techniques found in kata through the use of partners. Though under that definition it may actually be more accurate to classify this type of activity under the kumite banner rather than that of kata.