best practicesfontstypography
As an example: The Newton's Law gives
F=ma vs. dim F=MLT^{-2}
My question is: Should I typeset the "MLT" in \mathit shape?
You can contrast
\[\mathit{LT}\mathit{LT}\mathit{LT}\mathit{LT}\]
\[\mathit{L}\mathit{T}\mathit{L}\mathit{T}\mathit{L}\mathit{T}\mathit{L}\mathit{T}\]
the latter is more close together. Is there some tricks on using \mathit shape?
Or I should choose the \mathrm family, or even just the default math font?
As the author of siunitx I have some idea about the relative strengths of the various alternatives. There are various things that need to be done for units:
\kilo\metre rather than km: this allows special effects such as reformatting fractions 'on the go' (some people prefer to use literal input, and this ideally needs to be supported too).Many packages have been written to address one or other aspect of this question. For example, SIunits is good at providing semantic input, whereas SIstyle focusses on correct typesetting but leaves the input to the user. On the other hand, unitsdef sticks to doing only units and does not worry about other aspects.
The aim of the siunitx package is to cover all of the requirements above, and to provide a way that package behaviour can be altered. Thus it uses a series of key-value options that will change how the output is formatted. The options can be applied to the entire document or to an individual piece of input. It also is designed to work in either math or text mode equally well. I have also been very careful to provide up to date advice about the internationally-agreed units in the documentation of siunitx.
As a demo, using the latest release of siunitx the following all show off the package:
\documentclass{article}
\usepackage{siunitx}
\begin{document}
\begin{itemize}
\item \qty{100}{\degreeCelsius}
\item \qty{3e5}{\km\per\s} or \qty[per-mode = symbol]{3e5}{\km\per\s}
\item \unit{\newton\metre\squared\per\kilogram\squared} or
\unit[per-mode = symbol]{\newton\metre\squared\per\kilogram\squared}
\item \( \qty{10}{\kilo\hertz} = \qty{1}{\per\second\tothe{4}} \)
\item \qty[parse-numbers = false]{\sin(x)}{\metre}
\end{itemize}
\end{document}
There are a couple of notes to bear in mind if using siunitx. First, it requires e-TeX, which can be an issue with some publishers (even over 10 years after it was finalised!). Secondly, the formatting does take up some time. There are settings to turn things off but it's always the case that working by hand will ultimately be faster. However, the upside of clearer and more flexible input is in my opinion worth it.
One other point is that siunitx is under development, with bug fixes and new features (there is a list for v3.1). In contrast, both SIunits and SIstyle are depreciated: bug fixes only. The units and unitsdef packages have not been updated for many years.
a good and detailed answer can be found also here - although it's talking about web design, I think these are good guide lines also for printed documents: http://webdesign.about.com/od/fonts/a/aa080204.htm
Best Answer
Both, the SI-Brochure nr. 8 (section 1.3, p. 105) and DIN EN ISO 80000-1:2012-10 (chapter 5, p. 19) use upright capital and sans-serif letters for this.
Therefore you should write dimensions of quantities like this:
This yields:
Unfortunately, there is no sans-serif font for medium-weight Greek letters in the range of uni-code characters. But if you normally use italic capital Greeks in your document (
math-style=ISO), it will be distinguishable.Three other remarks on your OP:
$\mathit{LT}$and$\mathit{L}\mathit{T}$should (and do) look the same.\mathit{...}.[Q]means "the unit of Q".{Q}would signify "the value of Q" and for your case, it should bedim Q.$Q = \{Q\}\cdot[Q] \wedge \dim Q = \mathsfup{L}^\alpha \dots$.