# Concatenation symbol between two sets

I am searching fo an appropriate symbol in latex for the concatenation between two sets

Thanks,

I want a symbol like this in the following image

• I mean by concatenation that if A = \{ a_1, a_2, ..., a_t\} and B = \{ b_1, b_2, ..., b_s\}, then A concat B = \{ a_1, a_2, ..., a_t, b_1, b_2, ..., b_s\} – Ou Baï Sep 27 '14 at 8:38
• In school we used the $\cup$ for a set union. – quinmars Sep 27 '14 at 8:50
• What do you mean with "concatenation of sets"? To you mean union? Do you know how to symbol you want looks like? If so, please draw it (e.g. on martin-thoma.de/write-math/classify) and share the link / put an image online. If you don't know how the symbol you want looks like, then you should eventually rather ask on math.stackexchange.com. – Martin Thoma Sep 27 '14 at 8:54
• You can find pretty much every symbol for LaTeX here: LaTeX_symbols.pdf – Václav Pavlík Sep 27 '14 at 9:22
• @OuBaï: You seem to have managed to make an image of the symbol. How did you create that image? – Martin Thoma Sep 27 '14 at 9:45

A great resource for this kind of question is the opaquely named Detexify, at http://detexify.kirelabs.org/classify.html. You sketch a shape with the mouse and it lists the TeX symbols that look like it, along with package and mode information. It did a great job with my very clumsy rendering of your symbol, finding as top matches the same symbols proposed by egreg and LaRiFaRi:

Your symbol seems \smallfrown from amssymb, but raised up.

\documentclass{article}
\usepackage{amsmath,amssymb}

\newcommand{\tieconcat}{%
\mathbin{\mathpalette\dotieconcat\relax}%
}
\newcommand{\dotieconcat}[2]{% auxiliary macro, don't use it directly
\text{\raisebox{.8ex}{$\smallfrown$}}%
}

\begin{document}
$A\tieconcat B$

$A\sqcup B$
\end{document}

The symbol I prefer, though, is \sqcup that I showed at the bottom.

If you are able to use Lua- or XeLaTeX, you can just use the Unicode of this symbol which is U+2040. There will be quite a lot of fonts on your system that support this symbol. You could choose one, load the package fontspec and do: \newcommand*{\concat}{\fontspec{your-font-name}\mathbin{\text{\symbol{"2040}}}}.

However, it would be easier to use the command \tieconcat which is part of the unicode-math package. The fonts XITS and Asana do provide that symbol. This could look like the following:

% arara: lualatex

\documentclass{article}
\usepackage{unicode-math}

\begin{document}
\setmathfont{XITS Math}
$A\tieconcat B$
\setmathfont{Asana Math}
$A\tieconcat B$
\end{document}

If you want to use PDFLaTeX, you will have to use \frown from mathtools or MnSymbol or for a narrower version \smallfrown from amssymb.

You can reproduce your symbol by raising them a bit up. Just adapt the 0.9ex until you find it pleasing.

% arara: pdflatex

\documentclass{article}
\usepackage{amssymb}
\usepackage{mathtools}
\newcommand*{\upFrown}{\mathbin{\raisebox{0.9ex}{$\frown$}}}
\newcommand*{\upSmallFrown}{\mathbin{\raisebox{0.9ex}{$\smallfrown$}}}

\begin{document}
$A\upFrown B \upSmallFrown C$
\end{document}