# Symbol for disjoint union

I found two symbols for the disjoint union. One is the union with a dot and I can do it. The other possibility is to put a small 'D' inside the union and this is what I don't find in any list of symbols I've checked. Could some one help me with this??Thank you so much!

• Welcome! Why not use the one with the dot? – cfr Jul 10 '15 at 21:57
• And why not use $\coprod$ or $\bigsqcup$ or $\amalg$? – Bernard Jul 10 '15 at 22:10

A case for \ooalign. I provide two variants, in the first one, the D is in math mode; in the second one it is in sans-serif text-mode font (I like this one). The example code shows the symbol for all math styles:

The code:

\documentclass{article}
\usepackage{graphicx}

\newcommand\DUnion{
\mathop{\mathchoice
{\ooalign{$\displaystyle\bigcup$\cr\hss\scalebox{.65}{\raisebox{0.45ex}{$D$}}\hss}}
{\ooalign{$\textstyle\bigcup$\cr\hss\scalebox{.8}{\raisebox{0.5ex}{\tiny$D$}}\hss}}
{\ooalign{$\scriptstyle\bigcup$\cr\hss\scalebox{.45}{\raisebox{0.3ex}{$D$}}\hss}}
{\ooalign{$\scriptscriptstyle\bigcup$\cr\hss\scalebox{.38}{\raisebox{0.4ex}{$D$}}\hss}}
}
}
\newcommand\Dunion{
\mathop{\mathchoice
{\ooalign{$\displaystyle\bigcup$\cr\hss\scalebox{.65}{\raisebox{0.45ex}{\sffamily D}}\hss}}
{\ooalign{$\textstyle\bigcup$\cr\hss\scalebox{.9}{\raisebox{0.5ex}{\tiny\sffamily D}}\hss}}
{\ooalign{$\scriptstyle\bigcup$\cr\hss\scalebox{.45}{\raisebox{0.3ex}{\sffamily D}}\hss}}
{\ooalign{$\scriptscriptstyle\bigcup$\cr\hss\scalebox{.38}{\raisebox{0.3ex}{\sffamily D}}\hss}}
}
}

\begin{document}

$A\DUnion B\quad {\displaystyle A\DUnion B}\quad L_{A\DUnion B}\quad M_{L_{A\DUnion B}}$

$A\Dunion B\quad {\displaystyle A\Dunion B}\quad L_{A\Dunion B}\quad M_{L_{A\Dunion B}}$

\end{document}

• Are you sure about using \bigcup as a binary operator? – egreg Jul 11 '15 at 7:23