I have the following equation, where there is a lot of stuff under the sum symbol:

```
\begin{equation}
d(\vec{x},\vec{y})=
\sum_{Z_{xy}\in\vec{Z}_{xy},\forall x\in\vec{x},\forall y\in\vec{y}}
f(Z_{xy})
\end{equation}
```

In the resulting document, I find it kind of hard to read. Is there a way to write the equation to make the result more readable, e.g. putting the stuff under the sum symbol on different lines?

## Best Answer

You can use the

`\substack`

command from the`amsmath`

package, like this:However, the result still doesn’t look good, because of the extra spacing around the sum symbol:

To fix this, you can use the

`\mathclap`

command from the`mathtools`

package, like this:But perhaps you might be happy using

only`\mathclap`

, and not`\substack`

. The result looks good as long as the subscript is not too wide.The

`mathtools`

package also have several other useful commands for typesetting mathematics, including more commands for improving the display of subscripts and superscripts. I very much recommend taking a look at its documentation.