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It seems to be generally well accepted that the correct way to typeset a value with units is to separate the number from the units by a space, and write the units in an upright font. For example,

One hellameter is \( 1.0\times10^{27} \) m.

The symbol for 'micro-' is the Greek letter mu, but if you compile

At the telecom wavelength of \( 1.55\ \mu \)m ...

then the spacing will be correct and the 'm' will be upright, but the 'mu' won't be.

How do you produce an upright lowercase mu? More generally, how do you make any Greek letter appear upright?

share|improve this question
Care to revisit your answer decision? It looks like Joseph's answer is superior to the one you have currently selected, as evidenced by the comments and answers of Will, Joseph, and myself. In the end, it's your question, but you will get better answers in the future. if you give a little more time (about 48 hours is recommended) for answers to come in. – Kevin Vermeer Jul 29 '10 at 15:49
I agree- we should probably promote siunitx over SIunits as that package is being actively maintained and developed. – Sharpie Aug 19 '10 at 5:02
Thanks for a nice question! Please update siunitx as the right answer (I went to the trap of trying SIunits at first, because I was impatient to read the entire tread). – Mikko May 23 '12 at 15:51
up vote 68 down vote accepted

The siunitx package does this 'properly' without the user needing to worry


(Note: I am the author of siunitx, which is the successor to both SIunits and SIstyle.)

Of course, for the more general question about upright Greek letters then the upgreek package is indeed the best plan.

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Can you explain what you mean by 'properly,' and what it is the user might have needed to worry about with the SIunit package? – Michael Underwood Jul 29 '10 at 16:18
By 'properly', I mean that the standard settings for siunitx will use an upright font for the micro symbol. The symbols is supposed to be in an upright font: see the regulations from NIST (physics.nist.gov/cuu/Units) and the BIPM (bipm.org/en/si). The issues with the SIunits package stem from the fact that it doesn't have full control of the font used for printing (according to the regulations, units should be upright in roman font). It also doesn't have the flexibility that siunitx provides. – Joseph Wright Jul 29 '10 at 20:49
does siunitx work if someone spells that as meter? :) – Billy ONeal Sep 29 '10 at 5:41
Indeed it does: I am a realist! Of course, you can always add additional units using \DeclareSIUnit, for example to support specialist units (which may not be SI). – Joseph Wright Sep 29 '10 at 5:49
@Largh That's because it's showing semantics. You can use the abbreviations, so for example \SI{10}{\um} or \si{\um}, as explained in the documentation. – Joseph Wright May 23 '12 at 15:57

The upgreek package provides upright Greek letters from the Euler or Adobe Symbol fonts as additional math symbols, with proper scaling in super- and subscripts.

Another way to properly write micrometer is by using the SIunits package:

share|improve this answer
Thanks! Are all of those options needed for SIunits? I didn't notice any difference with or without them based on your example. – Michael Underwood Jul 28 '10 at 21:48
The upgreek package documentation is straightforward, and says that "the lowercase letters are named \upalpha, \upbeta etc., whereas \Updelta, \Upgamma etc. create upper case." – Michael Underwood Jul 28 '10 at 21:49
No, the first two can be used to control the use of white space, Grey and squaren can be specified to avoid conflicts with other packages you may be using. – rcs Jul 28 '10 at 21:50
siunitx is the successor to siunits – Will Robertson Jul 29 '10 at 2:55
That was rather my aim :-) – Joseph Wright Sep 28 '10 at 19:33

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