# What to use for itemize/enumerate/description type question

I have a lemma in which I want to say something like this:

Let f be a function which satisfies either

(A) f=0 and f is continuous, or

(B) f=1 and f is well-defined.

Then f is good.

My question is, what environment should I use for the two options (A) and (B)? Should I use enumerate, itemize or description, or something else? I may say later on "If f satisfies the case (A), then ..."

• If one knows what the counter name is being used by \item (which depends on what packages are loaded) one could do something like \renewcommand\theenumi{(\Alph{enumi})} – John Kormylo Aug 27 '15 at 13:17

The natural structure to use here is an enumerated list. Using the enumitem package you can easily change the counter representation to have the desired formatting:

\documentclass{article}
\usepackage{enumitem}
\usepackage{amsthm}

\newtheorem{lem}{Lemma}

\begin{document}

\begin{lem}
Let $f$ be a function which satisfies either
\begin{enumerate}[label=\textup{(\Alph*)}]
\item\label{ite:casea} $f=0$ and $f$ is continuous, or
\item\label{ite:caseb} $f=1$ and $f$ is well-defined.
\end{enumerate}
Then $f$ is good.
\end{lem}

\begin{proof}
If $f$ satisfies the conditions of Case~\ref{ite:casea} then\ldots\ On the other hand, if $f$ satisfies the conditions of Case~\ref{ite:caseb} then\ldots
\end{proof}

\end{document}