Guide to LaTeX (4th Edition) (Tools and Techniques

4.3. Lists 73
label. For the enumerate environment, this means that the corresponding
counter is not automatically incremented and the user must do the
numbering manually.
The optional label appears right justified within the area reserved for
the label. The width of this area is the amount of indentation at that level
less the separation between label and text; this means that the left edge
of the label area is flush with the left margin of the enclosing level.
It is also possible to change the standard labels for all or part of the
document. The labels are generated with the internal commands
\labelitemi , \labelitemii , \labelitemiii , \labelitemiv
\labelenumi , \labelenumii , \labelenumiii , \labelenumiv
The endings i, ii, iii, and iv refer to the four possible levels.
These commands may be altered with \renewcommand. For example,
to change the label of the third level of the itemize environment from ∗
to +, give
\renewcommand{\labelitemiii}{+}
Similarly the standard labels for the enumerate environment may be
changed. However, here there is an additional complication that there
is a counter for each enumerate level, named enumi, enumii, enumiii,
and enumiv. As explained in Section 8.1.4, the value of a counter can be
printed using one of the commands \arabic, \roman, \Roman, \alph,
or \Alph, where the style of each command should be obvious from its
name. That is, \Roman{xyz} prints the current value of the counter xyz
in upper case Roman numerals, whereas \alph{xyz} prints it as a lower
case letter (with a corresponding to 1 and z to 26).
These counters, together with the counter style commands, must be
used in the redefinitions of the label commands. For example, to change
the second-level label to Arabic numerals followed by ‘.)’, it is necessary
to give
\renewcommand{\labelenumii}{\arabic{enumii}.)}
which redefines \labelenumii to the value of counter enumii printed in
Arabic, plus the characters ‘.)’. In this way, all the numbering levels may
be changed. It is even possible to include more than one counter:
\renewcommand{\labelenumii}{\Alph{enumi}.\arabic{enumii}}
which will produce for every call to \item at level two the value of the
counter enumi as a capital letter followed by the value of counter enumii
as a number: that is, in the form A.1, A.2, . . . , B.1, B.2, . . . and so on.
If the new standard labels are to apply to the whole document, the
redefining commands should be included in the preamble. Otherwise,
they are valid only within the environment in which they appear.