# Long equation labelled by a symbol

To label a single symbol to long equation, we use \begin{split}...\end{split}:

   \begin{align}\label{eq1}
\begin{split}
H=\langle x_1,x_2,\cdots, x_n \colon & [x_i,x_j,x_k]=1,\\
& [x_i,x_j]^p=1 \rangle.
\end{split}
\end{align}


To label an equation by a symbol say (*), we use \tag{ } inside .

$$E=mc^2\tag{*}$$


Question: If I want to label a long equation by a single symbol, how to do it?

$$...$$ should be used for display math that consists of a single formula, i.e., has only one equation "number". split can be used within equation, and is recommended (read the documentation, please). so

$$\label{eq1} \begin{split} H=\langle x_1,x_2,\cdots, x_n \colon & [x_i,x_j,x_k]=1,\\ & [x_i,x_j]^p=1 \rangle. \end{split} \tag{*}$$


will do exactly what you want.

• Or aligned. But the main request is to also use something like \tag{<symbol>}.
– Werner
Mar 2, 2016 at 2:24
• sorry, I didn't get your your answer. where we use \tag here? Mar 2, 2016 at 2:25
• @pGroups -- sorry, not paying proper attention. fixed now. Mar 2, 2016 at 2:30
• @barbara: Thanks. (Actually, I was checking this by adding \tag{ } at different places inside \begin{equation..., but it was giving errors. Then I thought that there may be some different way for it, hence posted the question above.) Mar 2, 2016 at 3:10