# Nomenclatura-How to display one symbol used in two differents contexts or more

The following example builds one nomenclatura (the list of some importa symbols).

The problem I met is the following one : if one symbol is used in two contexts, this symbol appears two times (see the letter a in my example).

Is it possible to change this so as to obtain for example the letter a appears only one time in the nomenclatura following by list of the different uses of this letter ?

\documentclass{article}
\usepackage{nomencl}
\makenomenclature

\begin{document}

\section*{Main equations}

$$a=\frac{N}{A}$$%

\nomenclature{$a$}{The number of angels per unit area}%
\nomenclature{$N$}{The number of angels per needle point}%
\nomenclature{$A$}{The area of the needle point}%

The equation $\sigma = m a$%

\nomenclature{$\sigma$}{The total mass of angels per unit area}%
\nomenclature{$m$}{The mass of one angel} follows easily.

Let's try with another $a$... %
\nomenclature{$a$}{The area of the needle point}%

\printnomenclature

\end{document}


The solution given just after by Werner does the job but there is still one problem from my point of view.

a    The number of angels per unit area
The area of the needle point


it would be better to have something like...

a    - The number of angels per unit area
- The area of the needle point


Is it possible to do that ?

-

In the following example I played around with the sort order of nomencl by using the <prefix> command:

\nomencl[<prefix>]{<symbol>}{<description>}


However, it required to transform all the nomenclatures to the same type (string in this case). That is, using the prefix for each item (in text/non-math) so that they are sorted in the same group.

\documentclass{article}
\usepackage{nomencl}% http://ctan.org/pkg/nomencl
\makenomenclature

\begin{document}

\section*{Main equations}

$$a=\frac{N}{A}$$%

\nomenclature[a]{$a$}{The number of angels per unit area}%
\nomenclature[N]{$N$}{The number of angels per needle point}%
\nomenclature[A]{$A$}{The area of the needle point}%

The equation $\sigma = m a$%

\nomenclature[s]{$\sigma$}{The total mass of angels per unit area}%
\nomenclature[m]{$m$}{The mass of one angel} follows easily.

Let's try with another $a$... %
\nomenclature[a1]{}{The area of the needle point}%
\nomenclature[a2]{}{The distance to the moon}%
\nomenclature[a3]{}{The number of needles in a haystack}%
\nomenclature[a4]{}{The value of $pi$}%
\printnomenclature

\end{document}


In the above example, all items under the a nomenclature that should be printed without a, has been given a prefix a? where ? is a numeric to force some sort order.

Text-only nomenclatures can be used in the traditional form without the prefix <prefix>, like (say) \nomenclature{C}{This is a C, see.}; included in the above MWE. You'll notice that the \sigma entry has been sorted based on the text prefix s. This can be changed if needed.

Since there is no connection between the items in the List of Nomenclatures and the grouped sorting has been manually altered (via specifying a1, a2, ... for items using the same symbol as a), there is no way to easily accommodate the following request automatically:

Manually, however, it is no problem. Just add the respective dashed (-- or en-dash) before each item. This should not be a major drawback, since the nomenclature items are formatted and inserted manually in the document anyway:

\documentclass{article}
\usepackage{nomencl}% http://ctan.org/pkg/nomencl
\makenomenclature

\begin{document}

\section*{Main equations}

$$a=\frac{N}{A}$$%

\nomenclature[a]{$a$}{--\ The number of angels per unit area}%
\nomenclature[N]{$N$}{The number of angels per needle point}%
\nomenclature[A]{$A$}{The area of the needle point}%

The equation $\sigma = m a$%

\nomenclature[s]{$\sigma$}{The total mass of angels per unit area}%
\nomenclature[m]{$m$}{The mass of one angel} follows easily.

Let's try with another $a$... %
\nomenclature[a1]{}{--\ The area of the needle point}%
\nomenclature[a2]{}{--\ The distance to the moon}%
\nomenclature[a3]{}{--\ The number of needles in a haystack}%
\nomenclature[a4]{}{--\ The value of $pi$}%

\printnomenclature

\end{document}

-
Thanks for this explanation. Is there a way to have display some symbol before each item of the list ? – projetmbc Oct 9 '11 at 9:51
@projetmbc: I thought you were interested in removing the symbol before each item in the duplicated symbol. Do you want some symbol printed before each item in the list? Please provide more detail; perhaps even by editing your original question to include this information. – Werner Oct 9 '11 at 15:06
I've edited my first message so as to point what I'm looking for. – projetmbc Oct 9 '11 at 18:53
@projetmbc: See my revised answer. Hope this helps. – Werner Oct 9 '11 at 21:07
Thanks for this. – projetmbc Oct 10 '11 at 18:06