# Labeling lines (or columns) of tikzcd diagrams

I would like to be able to label (by number or a symbol) not only a commutative diagram as a whole, but also single lines of the diagram.

For example, in a diagram

\documentclass{article}
\usepackage{amsmath,tikz-cd}

\begin{document}

\begin{tikzcd}
0 \ar[r] & A\ar[r] \ar[d] & B \ar[r] \ar[d] & C \ar[r] \ar[d]& 0 \\
0 \ar[r] & A'\ar[r]  & B' \ar[r]  & C' \ar[r] & 0 \\
\end{tikzcd}

\end{document}


I would like to be able to label each row, say by $(\varepsilon)$ and $(\varepsilon')$, similarly to labeling equations etc. I do not want to label just the commutative diagram as a whole.

Is there a way how to do that?

Thanks in advance for any help.

Here's a possibility: you add a column, but remove some of the horizontal space.

\documentclass{article}
\usepackage{amsmath,tikz-cd}

\begin{document}

\begin{tikzcd}
\varepsilon\colon &[-3em] 0 \ar[r] & A\ar[r] \ar[d] & B \ar[r] \ar[d] & C \ar[r] \ar[d]& 0 \\
\varepsilon'\colon&[-3em] 0 \ar[r] & A'\ar[r]  & B' \ar[r]  & C' \ar[r] & 0 \\
\end{tikzcd}

\end{document}


• Thank you. That should be sufficient for my purposes. Is there a way how to refer to it in a text, by any chance? – PavelC Apr 13 '16 at 17:48
• Since they're manually added, I can't see the need for \ref. Besides, it would most easily conflict with the enclosing environment. – egreg Apr 13 '16 at 17:52