\begin{enumerate}
\item First item
\item Second item
....
\end{enumerate}
The enumerate environment produces a numbered list. Enumerations can be nested within one another, up to four levels deep. They can also be nested within other paragraph-making environments.
There must be at least one \item command within the environment.
Each item of an enumerated list begins with an \item command. The optional label argument of the \item command, if given, suppresses incrementing the counter. If not given the default labels are taken from the counters, enumi, enumii, enumiii, enumiv for the four allowed levels of nesting, respectively.
The numbering style for the enumeration is determined by the commands, \labelenumi, \labelenumii, etc., for the nested levels. These may be redefined with the \renewcommand command.
For example, to use upper case letters for the first level and lower case letters for the second level of enumeration:
\renewcommand{\labelenumi}{\alph{enumii}}