Kings and fat horses: Understanding muri, mura, muda

The “3 Ms”— muri, mura, muda — is among the most important concepts in lean production. Yet, the Ms are often misjudged.

The most common misunderstanding is to see lean only as a method to reduce waste  (“muda”). Those that start waste-hunting lean projects will not achieve break-through improvements and will never build a culture of continuous improvement. When Toyota developed the Toyota Production System, they learned early on that there are two other enemies of productivity; muri and mura. In my field studies of lean in numerous factories around the world, I have learned that the sequence of the words matter. To efficiently improve a process, muri should be attacked before mura, and mura before muda.

The English translations of muri, mura, and muda as used in a manufacturing settings are well established as “overburden,” “unevenness,” and “waste”. Although this is an accurate translation of the meaning, there is more to it. To learn more about the deeper meaning of the 3 Ms, I sat down with Hugo Tschirky, Professor Emeritus at ETH Zurich and an expert in Japanese culture and management. I was fascinated about what I learned, and would like to pass it on to my readers.

Note that I have not seen this kanji-level explanation of muri, mura, and muda anywhere else before. Also, be aware that interpretations of kanjis differ and that I cannot guarantee that this interpretation is correct. The meaning of a Japanese word is not always related to the meaning of the original Chinese characters. Thanks to Professor Masaru Nakano (Keio University, ex. Toyota), Professor Hajime Mizuyama (Aoyama Gakuin University) and Doctoral Candidate Mieko Igarashi (NTNU) for discussing this post with me prior to publication. All remaining errors are my own. Please comment below if you have similar or alternative explanations of the 3 Ms.


Muri (Hugo Tschirky 2017)Muri (無理) consists of two kanjis, which can be translated into “unreasonable” or “’impossible”. The first kanji “mu” (理) shows a fire that burns; it means that nothing is left. The second kanji “ri” (理) illustrates the “king (王) of the village (里)”, which is best translated as “reason” or “correct”. Putting “mu” before “ri”, you get “totally unreasonable”. Hence, muri means something that cannot be accepted. This is a general translation. In a manufacturing factory, we translate “muri” into overburden of machines, people, and processes. Because overload will make the production break down, it is “totally unreasonable”. Muri should be the first thing to reduce.


Mura (Hugo Tschirky 2017)Mura (斑) starts with the same phonetic sound as muri and muda, but note that its kanji is completely different. It consists of only one symbol that means uneven. There are at least two different interpretations of the kanji itself: It can be seen as a compound of two other kanjis, a simplified version of 𤤴 plus 文. 𤤴 means two pieces of jades merged together and the 文 in the middle symbolizes a man that have cut them in two dissimilar pieces. Alternatively, it can be seen as a man (文) in the middle of two kings (王), which would symbolize that unevenness is a king-level issue that must be treated seriously. If you have mura in your process, you will get uneven output. Unevenness is the enemy of balance and stability. In a manufacturing setting, it is the second thing to reduce.


Muda (Hugo Tschirky 2017)It is common to translate muda (無駄) into useless, unnecessary, or waste. Muda starts with the same kanji prefix as muri. As explained, “mu” (無) means something similar to “nothing”. The second kanji “da” (駄) consists of “horse” (馬) plus “fat” (太). In the middle ages, horses were of vital importance in the Far East. The horse should be fit and strong. The worst thing you could have was a fat horse. You cannot use a fat horse, yet you must care for and feed it. Note the very common Japanese word “dame” (駄目), which literally means to look (目) at fat horses and is usually translated to “no good” or “don’t do it”. Fat horses are waste and must be avoided, and you should certainly not just stand and stare at them. Luckily, Taiichi Ohno has helped us describe what “fat horses” look like in factories: Transportation, Inventory, Motion, Waiting, Overproduction, Over-processing, and Defects. You must avoid muda, but remember the sequence of muri, mura, muda.

Further reading

  • Ohno, T. (1988). Workplace management: Productivity Press.
  • For the usual definition of the 3Ms, see LEI’s Lean Lexicon.
  • Michel Baudin has several good posts about muri, mura, and muda.
  • Prof. Christoph Roser explains the origin of Muri, mura and muda: the three evils of manufacturing.
  • Netland, T. H., & Powell, D. J. (2017). A Lean World. In T. H. Netland & D. J. Powell (Eds.), The Routledge Companion to Lean Management, Routledge

Do you agree or disagree with my examination of muri, mura, muda? Please leave your comments below. Did you enjoy this explanation? Then you probably will like this post about 5S too.

8 thoughts on “Kings and fat horses: Understanding muri, mura, muda

  1. Alliteration here trumps etymology. Three short words all starting with “mu” make a memorable phrase. Just by reciting “Muda, Muri, Mura” you can remind team members of points they should pay attention to.

    The meaning of the words in everyday life then helps operators, managers and engineers communicate. People in Japan refer to unnecessary things as “Muda”; someone who tries too hard is doing “Muri”; and “Mura” does mean uneven.

    Japanese people usually don’t pay attention to etymology any more than we do.

    • Good point about alliteration, Michel! Thank you. Surely that is one reason for the choice of words. According to my Japanese sources, etymological explanations are however sometimes used in Japan to get a message or meaning across. In that regard, the Chinese characters are arguable more exciting than the Latin alphabet. In everyday life, your are correct that Japanese usually do not pay attention to it.

  2. Thank you for share this very important lean topic with us. I completely agree with you. The correct sequency of attack is Mura, Muri and Muda. If you do not this the Muda will come back.

  3. Original explanation about MURI, MURA and MUDA. The calligraphies are nice and it’s always funny to see where the words we’re using are coming from.
    The sequence we’re using in our company is : MURI then MURA then MUDA… We might discuss about this sequence in another post.

    • Thank you. All calligraphies are by Prof. Tschirky. The sequence you are using in your company is the same that I would recommend.

  4. If you look at mura. It is a man cutting a jade into two piece. If you look carefully the jade is split to two word n one small one big. So it turn no balance

  5. I got detailed and excellent feedback from a knowledgeable colleague in Japan that enhances the quality of this blog post. The following are the words of Prof. R. Kosuge at Ritsumeikan University in Osaka, Japan:

    First, Chinese characters (kanji) are not used in practice. Instead, katakana, another writing system mainly used for words imported from foreign languages, is used. I think the main reason behind this is that these words have specific meaning or nuance in the workplace, although each word is heavily used in daily life. (By the way, the character “斑” can rarely be seen in daily life.) So, in Japan, muri mura muda is described as follows: ムリ ムラ ムダ. Taken together, they are sometimes called “3ム”

    Another issue is the order of words (not sequence of implementation). Although there are different versions, the most well-accepted order is muda-mura-muri. This highlights muda as the primary target of kaizen. Also, because “darari (ダラリ)” (muda’s “da” plus mura’s “ra” plus muri’s “ri”) means flabby (i.e. opposite of kaizen attitude) in Japanese, it’s easy for Japanese people to memorize the words.

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