# Starred multiline environments don't work

This is a "asking a question so I can answer it" question, hope no one minds.

As you may know, LaTeX provides two versions of most of its equation-like environments: One which updates the equation-numbering-counter and displays the equation number, and one which does not; for minor equations which you don't want to number. For example, this is the difference between multline and multline*.

Since math.SE doesn't provide equation numbering, I habitually type the starred versions of these commands when using math.SE. This then causes all kinds of bugs, which frustrate me until I rewrite the equation in another manner. What should I do?

Here is a list of environments to which this question might be relevant (cribbed from Figure 5.1 in Gratzer's book):

equation, gather, multline, align, flalign, alignat


I only checked equation and multline.

• Hmmm... I usually use \begin{align*}....\end{align*} and have no problem. However, if I don't go into math mode first, then there are all sorts of problems, requiring escape characters (e.g., \\ for end of lines, etc). Commented Jun 2, 2011 at 18:22
• Commented Oct 24, 2013 at 6:53

## 2 Answers

I don't see any problems.

## Equation

Here is an example without the star:

$$X = Y$$


$$X = Y$$

Here is an example with the star:

\begin{equation*} X = Y \end{equation*}


\begin{equation*} X = Y \end{equation*}

## Align

Here is an example without the star:

\begin{align} X &= Y \\\\ Y &= Z \\\\ \therefore X &= Z \end{align}


\begin{align} X &= Y \\ Y &= Z \\ \therefore X &= Z \end{align}

Here is an example with the star:

\begin{align*} X &= Y \\\\ Y &= Z \\\\ \therefore X &= Z \end{align*}


\begin{align*} X &= Y \\ Y &= Z \\ \therefore X &= Z \end{align*}

## Aligned

Aligned is meant to be used in mathmode, and so avoids needing the doubled backslashes:

\begin{aligned} X &= Y \\ Y &= Z \\ \therefore X &= Z \end{aligned}


\begin{aligned} X &= Y \\ Y &= Z \\ \therefore X &= Z \end{aligned}

• Note the difference: You include the align and align* environments in double dollars. If you don't use these double dollar signs, the line breaks \\  should be replaced triple backslashes \\\  (one backslash is an escaping character).
– t.b.
Commented Jun 2, 2011 at 17:54
• @Theo: already fixed. :-) In latex, it is an error to use align in mathmode, so I switched to aligned. Commented Jun 2, 2011 at 17:56
• Huh. I'm confused, because I definitely had examples with multline* breaking, and I was very happy when this fixed it. But now I can't replicate them. Commented Jun 2, 2011 at 19:06

If you omit the star, there will be no equation number, and everything works fine.

• It might work if you escaped the star with a backslash. Commented Jun 2, 2011 at 16:13
• @qia this shouldn't be necessary, as we modified the source code to explicitly ignore anything inside  blocks a while ago. Commented Jun 3, 2011 at 9:37
• @Jeff: In TeX, you use with no dollar signs, so people are probably trying to use it without dollar signs here. I always use dollar signs and aligned (I had to edit my answer to make my code work not only on math.SE but also in latex). The non-dollar signed snippets in my answer are (now) all valid tex (except for doubled backslashes in the align example). To my mind, the double dollar is good enough. Commented Jun 3, 2011 at 23:08