Too deeply nested

This error appears when you start a LaTeX list.

LaTeX keeps track of the nesting of one list inside another. There is a set of list formatting parameters built-in for application to each of the list nesting levels; the parameters determine indentation, item separation, and so on. The list environment (the basis for list environments like itemize and enumerate) “knows” there are only 6 of these sets.

There are also different label definitions for the enumerate and itemize environments at their own private levels of nesting. Consider this example:

\begin{enumerate}
\item first item of first enumerate
  \begin{itemize}
  \item first item of first itemize
    \begin{enumerate}
    \item first item of second enumerate
    ...
    \end{enumerate}
  ...
  \end{itemize}
...
\end{enumerate}

In the example,

• the first enumerate has labels as for a first-level enumerate, and is indented as for a first-level list;
• the first itemize has labels as for a first level itemize, and is indented as for a second-level list; and
• the second enumerate has labels as for a second-level enumerate, and is indented as for a third-level list.

Now, as well as LaTeX knowing that there are 6 sets of parameters for indentation, it also knows that there are only 4 types of labels each, for the environments enumerate and itemize (this “knowledge” spells out a requirement for class writers, since the class supplies the sets of parameters).

From the above, we can deduce that there are several ways we can run out of space: we can have 6 lists (of any sort) nested, and try to start a new one; we can have 4 enumerate environments somewhere among the set of nested lists, and try to add another one; and we can have 4 itemize environments somewhere among the set of nested lists, and try to add another one.

What can be done about the problem? Not much, short of rewriting LaTeX — you really need to rewrite your document in a slightly less labyrinthine way.

FAQ ID: Q-toodeep