defining equation variables as a caption

Question

I want to define a couple of variables in a list alongside a equation. Here's my current code

\begin{figure}
\[ e = m c^2 \]
\begin{description}
    \item[e] energy
    \item[m] mass
    \item[c] light speed
    \end{description}
\end{figure}

This mostly works, but the text doesn't align with the figure, and the font is too big compared to the equation.

Adapting the code from this question mostly works, but I can't use \description and text is interpreted as a formula.

Is there a better way to do this?

Related/duplicate: How to provide a definition for symbols in a LaTeX math equation? — Werner, Jun 27 '13 at 06:26
When you say "alongside" do you mean "together with" or "to the right of"? — Andrew Swann, Jun 27 '13 at 06:33

score 9 · Accepted Answer · edited Jun 12 '17 at 17:15

I would use a simple table (environment tabular), then it is easier to control the alignment. Also the line spacing is more compact and can be controlled by redefining \arraystretch.

\documentclass{article}
\usepackage{array}

\begin{document}
\begin{figure}
  \centering
  \[ e = m c^2 \]
  \begin{tabular}{@{}>{$}l<{$}l@{}}
    e & energy\\
    m & mass \\
    c & light speed\\
  \end{tabular}
\end{figure}
\end{document}

Remarks:

@{} suppresses the \tabcol spacing, here at the left and right side of the table.
>{$} and <{$} is a feature of package array that allows to add $s for the first column automatically.
The font size is the same as in the formula. If you want to have a smaller font, then you can add \small, for instance.

score 6 · Answer 2 · edited Jun 10 '17 at 12:50

\documentclass[preview,border=12pt,varwidth]{standalone}% change it to your own document class

\usepackage{array,tabularx}

\newenvironment{conditions*}
  {\par\vspace{\abovedisplayskip}\noindent
   \tabularx{\columnwidth}{>{$}l<{$} @{\ : } >{\raggedright\arraybackslash}X}}
  {\endtabularx\par\vspace{\belowdisplayskip}}

\begin{document}
Most people know the formula
\[
E \ne mc^2
\]
where
\begin{conditions*}
 E  &  energy produced by drinking 5 gallons of bear and eating 10 kilograms of sausage (just to show multiline description)\\
 m  &  mass of the food \\
 c  &  speed of light
\end{conditions*}

\end{document}

enter image description here

defining equation variables as a caption

2 Answers2