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Five Ri


Taiichi Ohno’s TPS books have many “puns.” Very often he selects these words to send us a message.


Inside these books, five Japanese words ended with “Ri” are used.


“Ri (理)”

A symbol frequently used in Japanese that has a significant meaning. This symbol, “Ri (理),” represents Science, Logic, or Order. It is also the core concept of Eastern philosophy. It means “Correct way as a human.”


When I collect them, they tell a story about the importance of science and logic. Those five words are;

1. Muri 無理

2. Genri 原理

3. Seiri 整理

4. Gouri 合理

5. Shuuri 修理




1. Muri 無理

Muri appears as part of “Muri, Mura, Muda.” Here “Muri” is understood as overburden or hard work. But the thinking of “Muri” should go beyond such a simple definition. This symbol, 無, means empty, does not exist. It is based on eastern philosophy or religion. By understanding the meaning of 無, the meaning of Muri should be following;

  • No science or logic

  • Ignoring the correct way as human

Running a factory without standardized work is a “Muri” condition. Here the standard is not just a paper. The standardized work needs to be repeatable. Everybody needs to have one. There is a clear point where they can call help when needed. Without the support, “Muri” will continue to be with the people. “Muri” exist not only with people. Machine without proper maintenance. Material without assigned location. Undefined quality methods. All of these are “Muri” conditions.



2. Genri 原理

Genri means principle. Genri appears as part of the 5 Gen doctrine. It is Genba (現場), Genbutsu (現物), Genjitsu (現実), Genri (原理), Gensoku (原則). These are the principles of problem-solving activities, which Genri is the principle of science. When we conduct problem-solving, we should understand the principle of science, and we should not violate them. This 5 Gen doctrine applies to management, too. Strictly speaking, this 5 Gen doctrine does not originate from TPS. Instead, it is thinking spread by Tomozou Kobata, from Nippon Denso.



3. Seiri 整理

Seiri is the first “S” of the 5S. As I have posted on my previous blog, Seiri is not just removing unnecessary items, but it is about;

  • Organize based on science/logic

  • Organize the science/logic

Very often, different functions add tasks that contradict each other. Quality might add inspection work that is not included in the standardized work. Maintenance schedules their work while the production planning fully loaded the factory on the same day. An individual needs to attend multiple meetings at the same time. These are examples of unorganized science or logic causing chaos on the shop floor. The shop floor manager needs to organize these science and logic in a followable and repeatable way on the shop floor. If contradicting, the shop floor manager can stop and pull the functional managers to solve the issue.



4. Gouri 合理

Gouri means “rational.” The rare translation happened in Ohno’s book “Workplace management,” Gouri was translated as Kaizen. Is rational the same as Kaizen? It is a tricky question. As far as I understand, Ohno was using the word “rational” when a plant is following TPS philosophies. Rationalize sometimes means to fire people, and Ohno never used it in such meaning.

The critical point of Ohno’s message is that not all improvements match TPS philosophies. Improved the operator’s motion but increased the waiting time (Isolated Island). Speeding up the machine faster than takt time and disconnecting the flow. Efficiency went up but destroyed quality. These are examples of non-rational improvements. Ohno is constantly challenging not just to improve but in a rational way.



5. Shuuri 修理

Shuuri 修理 means repair. There is another word that can be translated as repair is Shuuzen 修繕. If I choose a better choice for repair, I will pick Shuuzen 修繕. This is because 繕 means mend, the left side is a string, and the right side means good. It represents fixing a cloth with a string.

The symbol of 修 Shuu means to master or learning of a skill. That means 修理 means master or learning the science or the logic. This is another reminder that we should not just repair but also understand the science or logic of defects, breakdowns, or problems to manage the future better.


Let me summarize these words.

1. Muri 無理 = non-existence of science or logic

2. Genri 原理 = principle of science

3. Seiri 整理 = organize based on science or logic / organize the science or logic

4. Gouri 合理 = rational (an improvement that matches TPS philosophies)

5. Shuuri 修理 = master or learning the science or logic

Many other Japanese words use the symbol “ri 理.”

For example, Teiri 定理 = Theorem, Rinri 倫理 = Ethics. Somehow for such words, Ohno did not use these words. I feel some intention behind these selections since they were extremely cautious about selecting words.

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