How can I add a (*) to the align environment with some regular equation in the center?

It's so I can type afterwards, "By (*), ..."

  • Please help us to help you and add a minimal working example (MWE) that illustrates your problem. It will be much easier for us to reproduce your situation and find out what the issue is when we see compilable code, starting with \documentclass{...} and ending with \end{document}.
    – user31729
    Dec 31, 2014 at 19:07
  • 6
    You're probably interested in \tag{*}\label{eq:label} and then use \eqref{eq:label} elsewhere in your document.
    – Werner
    Dec 31, 2014 at 19:07
  • Do you really want a (*) or an equation number?
    – user31729
    Dec 31, 2014 at 19:07
  • 1
    @ChristianHupfer, it is not rare to use some symbols for some very important equation.
    – Sigur
    Dec 31, 2014 at 19:10
  • @Sigur: Yes, I do that in hand-written equations as well -- depends on the topics, I believe...
    – user31729
    Dec 31, 2014 at 19:11

1 Answer 1


amsmath - loaded if you're using an align-like environment - provides \tag{<stuff>} where you can place whatever you like in the "equation number". Perhaps the following is what you're after:

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  f(x) &= ax^2 + bx + c \\
  g(x) &= x^3 - 1 \tag{$\star$}\label{eq:starred}
It should be clear from~\eqref{eq:starred} what you're after.


You can also use this with another align-like environment, or even equation.

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