AZERTY-style keyboard layouts in France and Belgium have a dedicated key for typing the Greek small letter mu (μ). While not having a dedicated (μ) key, keyboards in Germany, Denmark, Finland, Iceland, Norway, and Sweden provide a means to enter (μ) using composite gestures. Why is this one lowercase Greek letter so significant?

By contrast, the keyboards in Spain, Portugal, Italy, UK, and Ireland do not have a (μ). Why is this one Greek letter so important to French, German, and Nordics? How is it considered part of a standard user experience? Why not the Greek letter pi (π) or some other letter altogether?

And why do the Italians, who are geographically closer to the Greeks than the French, not have that letter?

For easy reference, Wikipedia's article that compares keyboard layouts is here.

Update: Some people have asked what the link is with UX, well I thought that was obvious but if it is not then I will go beyond the scope of the original question and elaborate the technical problems that are at its base - this μ key and also some other special keys on European keyboards like the "squared" and "cubed" keys (which are not present on US keyboard layouts) give problems in Firefox browsers on the handling of the keydown event in JavaScript. AZERTY layouts is what I have been able to test from the European keyboards and it is here that I observe the problem.

While IE and Chrome produce some form of numeric key code, allowing to identify which key the user pressed, in Firefox this is "undefined" (it isn't even a numeric value). I find it hard to accept that the presence of such a key on these keyboards should not be questioned - if there were only 105 keys on a keyboard and a whole group of countries decide to standardize THE GREEK LETTER MU as one of them, there has to be a reason for that. There should be a good reason for that, and I'd like to know what that is.

If I need to write code to especially cater to these keys that Firefox refuses to identify, it will be at a certain cost. If I ignore the keys in keydown but handle them only in keypress there is also a potential inconvenience to my users in France, Germany, and the Nordic countries due to reduced functionality. Knowing why this region standardized on this one letter (even if there are only historical reasons) would help me to weigh these costs.

  • Do I write this with Ctrl + Alt + M? When yes, Swiss Keyboards also don't have it... Commented Jun 6, 2014 at 10:49
  • 3
    µ is sometimes used in the metric system, like µm for 1*10E-6 meters. But talking as a german, we barley use µ.
    – Mirco
    Commented Jun 6, 2014 at 10:49
  • 1
    As a French, we don't use it either. As @verbose-mode said, it can be used for 1*10E-6, but you don't use it on a daily basis at all. Maybe some scientists do. Same goes for the character ¤ (Alt Gr + $), I don't think it's really used.
    – refreshfr
    Commented Jun 6, 2014 at 14:55
  • 1
    I'm Swedish and I haven't used the symbol since Uni. Interesting question but I don't see how it relates to UX.
    – Babossa
    Commented Jun 7, 2014 at 9:06
  • 1
    @DavidMulder your comment is false, please check commons.wikimedia.org/wiki/File:AZERTY_keyboard_layout.JPG. Also see apprendre-informatique.com/uploads/210_azerty.jpg. It may be that only the French and Belgian keyboards have this issue, and that German and Nordic keyboards act as you have written in your comment. With the French system it is a full key dedicated to the Greek letter mu, in some cases with shift, in others not.
    – Mishax
    Commented Jun 9, 2014 at 21:56

2 Answers 2


The mu character, µ, is used as a special symbol in many academic fields. Most known is probably its meaning for representing one-millionth (10-6). However, the character has many other meanings as well in measurement, mathematics, physics and engineering, computer science, chemistry, meat science, pharmacology, orbital mechanics, music, software, cameras and linguistics. Because of the wide range of use, it’s probably evaluated as a nice-to-have character on the keyboard, even if it requires extra effort to use it.

In the online game RuneScape the µ character, typed using Alt Gr + M, forced nearby players to log out. A handy cheat if you run into trouble.

The alternative graphic key Alt Gr was first introduced as a means to produce box-drawing characters back in the days when the space used for all characters where the same. You could then draw tables or other more advanced graphics using these characters even if it was very time consuming. This style in writing can still be seen in readme-files using simple text editors or Console applications with a fixed width character sizes.

Interestingly scanning through the article on the Alt Gr key on Wikipedia gives some insight in the difference in keyboard layouts in different regions. The US-international, South Slavic Latin, Belgian, Finnish, German, Nordic, Estonian keyboard layout uses the µ character but UK & Ireland, French, Italian, Latvian, Macedonian, Polish and Romanian doesn’t.

It looks like linguistic more than anything else does where Germanic languages uses the µ but Italic (Latin), Slavic and Baltic doesn’t. From the image above, this looks true apart from UK & Ireland.

enter image description here

So why not UK & Ireland? One guess is historical reference starting with the Boston Tea party leading to the US Independency from the British Empire. However, that seems farfetched. Maybe because UK & Ireland keyboards only print out two characters (other than vowel accents) are the Euro sign, €, and the broken pipe sign ¦ where you use the AltGr key.

Nevertheless, does this mean that the µ sign cannot be accessed from a British keyboard? No, if you use a British keyboard you can still type µ using Alt Gr + M, it just isn’t printed on the keyboard. Often we find this “problem” on Apple keyboards as well, where characters are hidden rather than printed on the keyboard to make it look cleaner. Whether or not this is good or bad for user experience depends on context. However, if you use it a lot, you will learn how to access it – and eventually your muscle memory will help you.


  • 1
    Benny, I've done a bit of digging and I suspect there may be an additional reason why especially the French dedicate an entire key to the micro sign on these keyboards and that is (one) the development of the SI metric system specifications appears to have been historically driven by the French, (two) there is only one metric prefix that is not a latin character, namely mu for micro, and (three) mu for micro was adopted as part of SI in 1960, about when the French were probably establishing their de-facto keyboard standard on digital devices.
    – Mishax
    Commented Jun 10, 2014 at 12:41
  • 1
    @Mishax That sounds great! You should post that as an answer then! Commented Jun 10, 2014 at 12:46

For the reason why the µ was placed in the AZERTY french keyboard: https://fr.wikipedia.org/wiki/Micro_(préfixe_du_Système_international_d'unités) (wiki, french) mentions some sources. Indeed SI seems the most important motivation.

My translated summary: when the IBM PC was marketed to France, the engineer in charge of localization insisted that this symbol was included in the keyboard, with the reasoning that "it would be unusual that in the country which gifted the SI system to the world, we would be at the eve of the 3rd millennium and unable to use it with a PC".


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.