Sign up ×
TeX - LaTeX Stack Exchange is a question and answer site for users of TeX, LaTeX, ConTeXt, and related typesetting systems. It's 100% free, no registration required.

I often find myself wanting two or more conditions below a sum, supremum, limit, etc. Currently, the only way I know to typeset this is using an \underset inside another \underset. For example,

\|A\|= \underset{\underset{\|\eta\|=1}{\|\xi\|=1}}{\sup} |\langle A\xi, \eta \rangle|


\underset{\underset{i_1+\dots+i_k=n}{i_1<\dots<i_k}}{\sum} x_1^{i_1} \dots x_k^{i_k}.

What I don't like about this is that the two lines under the sum, sup, lim, or whatever end up a different size, and I'd really like them to be equal. Is there a more flexible way to create multiline expressions under these symbols? (I tried putting a \\ inside the first argument of \underset, but it didn't work.)

share|improve this question
Welcome to! A tip: you can use backticks ` to mark your inline code as I did in my edit. – doncherry Jul 7 '11 at 14:05

1 Answer 1

You could use \substack or the subarray environment of the amsmath package.

For example:

\|A\|= \sup\limits_{\substack{\|\eta\|=1\\\|\xi\|=1}} |\langle A\xi, \eta \rangle|

You can omit \limits in displaymath mode. Of course \substack and subarray can also be combined with \underset.

Here's an example for \underset with subarray:

  i_1+\dots+i_k=n \\
  \end{subarray}}{\sum} x_1^{i_1} \dots x_k^{i_k}.

With subarray you can achieve left alignment by specifying l instead of c. r However, r doesn't work for right aligment, if one expects that.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.