# How to use multiple \label across multiple \align* environments?

For long calculations, I have two align* environments for two equations.

I have as an example

\documentclass{article}

\usepackage{amsmath}
\usepackage{nccmath}

\begin{document}

\begin{align*}
\label{Sum 1}1+2=3
1+2=3
1+2=3
1+2=3
1+2=3
1+2=3
1+2=3
\end{align*}
\\
\begin{align*}
\label{Sum 2}3+4=7
3+4=7
3+4=7
3+4=7
3+4=7
3+4=7
\end{align*}

\end{document}


When I try to compile, it says there is an ams error from using "multiple label's" which means it somehow thinks both align* environments are on the same line even though they can't be. I want to use align* because I only want one label for an entire equation, I do not want to have to type \nonumber for every single line in a regular align environment.

• use align* instead of align Jan 5, 2019 at 22:53
• When I use \align* it has no labels at all, I have to use \intertext which doesn't update with changes for cross referencing. Jan 5, 2019 at 22:55
• it is \begin{align*} not \align* you could use \tag to add a label I can not guess what you mean by \intertext which works the same way with align and align* Jan 5, 2019 at 22:58
• sorry no we are suggesting that you make your question clear enough that people can help you, but if you would rather not, that is OK too. Jan 5, 2019 at 23:00

Just spelling out @DavidCarlisle's comment. (Your code does not compile because there is no \documentclass and you have \usepackages after \begin{document}. Nor does it make too much sense using align the way you do, so I assume you forgot to add multiple \\.)

\documentclass{article}
\usepackage{amsmath}
\usepackage{nccmath}
\begin{document}
\begin{align*}
1+2&=3\\
1+2&=3\\
1+2&=3\\
1+2&=3\\
1+2&=3\\
1+2&=3\\
1+2&=3\label{Sum_1}\tag{1}
\end{align*}

\begin{align*}
3+4&=7\\
3+4&=7\\
3+4&=7\\
3+4&=7\\
3+4&=7\\
3+4&=7\label{Sum_2}\tag{2}
\end{align*}
The equations under \eqref{Sum_1} are at least as illuminating as those under
\eqref{Sum_2}.
\end{document}


• I also have the article document class, but individual labels don't work. Why does adding tag do anything? Jan 5, 2019 at 23:46
• @user14554 align* produces equations without labels. To add a label you can use \tag. (IMHO the cleaner way would be to use align and \notag for all the lines that should not get a number, but this is a matter of taste.)
– user121799
Jan 5, 2019 at 23:56