enumerate

enumerate is the environment for an ordered list — one whose items are numbered. You wrap entries in \begin{enumerate} … \end{enumerate} and start each one with \item. The numbers are generated automatically, and when you nest lists the format changes with the depth: 1. → (a) → i. → A.. This page covers how the automatic numbering works, the default format at each level and the counters and commands behind it, cross-referencing an item, changing the starting number, and the easy formatting the enumitem package gives you.

Basic usage

Inside an enumerate environment, each entry starts with \item. LaTeX assigns the numbers for you, so you never type “1.” or “2.” yourself. Everything from one \item to the next (or to \end{enumerate}) is the body of that entry; you may break lines and indent freely — LaTeX aligns the number and the left indent. Numbering restarts at 1 with each use of the environment.

\begin{enumerate}
  \item 材料を量る
  \item 生地を混ぜる
  \item 型に流して焼く
\end{enumerate}

This sets three entries labelled “1.”, “2.”, and “3.” at the head of each line. enumerate is a standard LaTeX environment — no package required. When you want markers instead of numbers, reach for itemize; for a labelled definition list, use description. At least one \item is required, and you cannot have body text without a leading \item.

Default numbering and levels

enumerate nests up to four levels deep, and the number format changes automatically with the level. In the standard classes (article and friends) the defaults are: level 1 an Arabic numeral with a period, 1.; level 2 a lowercase letter in parentheses, (a); level 3 a lowercase Roman numeral with a period, i.; and level 4 an uppercase letter with a period, A..

Each level has a counter and two commands that display it. The integer counters that do the counting are enumi, enumii, enumiii, and enumiv (the i / ii / iii / iv are Roman numerals naming the level). The command that formats a counter into the number text is \theenumi … \theenumiv, and the command that typesets it as the head-of-line label is \labelenumi … \labelenumiv. By default \theenumi, for example, is defined as \arabic{enumi} (an Arabic numeral), and \labelenumi adds the period to make 1..

To change only the look of the numbers, redefine the format command with \renewcommand. The commands that render a counter in a given style are \arabic (1, 2, 3), \alph (a, b, c), \Alph (A, B, C), \roman (i, ii, iii), and \Roman (I, II, III). For instance, to set level 1 as uppercase Roman numerals I, II, III:

\renewcommand{\theenumi}{\Roman{enumi}}
\begin{enumerate}
  \item 第一の論点
  \item 第二の論点
\end{enumerate}

Now level 1 reads “I.”, “II.”, and so on. Because \labelenumi is built on \theenumi by default, redefining \theenumi brings the head-of-line label — and the number returned by the cross-reference \ref below — into the same style. When you want to shape the surrounding punctuation (the period or parentheses) as well, redefine \labelenumi instead. Designing labels this way is covered in depth on the “Custom labels” page.

Referencing items

You can cross-reference an item of a numbered list: put a \label{key} in the body of the \item, then call \ref{key} elsewhere to print that item’s number. Because LaTeX manages the numbers, the reference automatically tracks the right value even if you add or reorder items. The format \ref returns follows that level’s \theenumi-family definition. For the page number, use \pageref{key}.

\begin{enumerate}
  \item 仮説を立てる
  \item 実験で検証する\label{step:test}
  \item 結果をまとめる
\end{enumerate}
手順~\ref{step:test} で測定したデータを使う。

Here the second item carries \label{step:test}, and the later sentence’s \ref{step:test} resolves to “2”. If you load the hyperref package, that reference becomes a clickable link that jumps to the item. As usual, resolving references generally takes two compilation passes. Cross-referencing in general is covered on the “Cross-references (\label and \ref)” page.

Changing the starting number

To start the numbering somewhere other than 1, set the counter inside the list with \setcounter. Since \item increments the counter before typesetting the entry, the trick is to give a value one less than the number you want. To start at 5, for example, write \setcounter{enumi}{4}.

\begin{enumerate}
  \setcounter{enumi}{4}
  \item この項目は 5 番になる
  \item 6 番
\end{enumerate}

The \item right after \setcounter{enumi}{4} becomes “5.”, and the next entry “6.”. To adjust deeper levels, set enumii, enumiii, or enumiv the same way. When your real goal is to close a list and later continue the numbering in a separate list, the enumitem package’s resume, described next, is easier and more reliable.

Easy formatting and continuation with enumitem

When you want fine control over the number format, the enumitem package is cleaner than hand-writing \renewcommand. Load it with \usepackage{enumitem} and you can set the format directly with a label= option on the environment. Inside label=, the starred forms \arabic*, \alph*, \Alph*, \roman*, and \Roman* stand for the current item number. For instance, label=(\alph*) produces (a), (b), and so on.

\usepackage{enumitem}
% ...
\begin{enumerate}[label=(\alph*)]
  \item 小文字を括弧で囲んだラベル
  \item 二つめの項目
\end{enumerate}

enumitem also makes starting and continuing easy. start= sets the first number directly (no “subtract one” as with \setcounter), and resume continues the numbering from the previous list instead of restarting. This keeps the sequence intact even when a paragraph of explanation or another figure breaks the list apart.

\begin{enumerate}
  \item 最初のリストの一つめ
  \item 二つめ
\end{enumerate}
間にはさむ説明の段落。
\begin{enumerate}[resume]
  \item 番号は 3 から続く
  \item 4 番
\end{enumerate}

With resume, the second list continues as “3.”, “4.”. You can also set just the starting number, as in start=10, or combine it with label= to control the format too. The spacing controls, inline lists, and reference labels that enumitem adds are gathered on the “enumitem” page.

A worked example

Finally, an example that combines what we have seen. We build a list of steps, attach a \label to one of them, and refer to its number from outside the list with \ref. Because LaTeX owns the numbering, the reference follows automatically even if you reorder the steps.

実験は次の手順で進める。
\begin{enumerate}
  \item サンプルを室温に戻す
  \item 重量を記録する\label{step:weigh}
  \item 溶媒を加えて撹拌する
  \item 一晩静置する
\end{enumerate}
手順~\ref{step:weigh} の値を、最終的な収率の計算に用いる。

In the output, the four steps line up numbered “1.” through “4.”. The second one, “Record the weight,” carries \label{step:weigh}, so the \ref{step:weigh} in the sentence after the list resolves to “2,” reading “the value from step 2…”. If you later insert “Inspect the apparatus” as a new first step, the target drops to third — but \ref updates itself to “3” automatically. That is the chief payoff of letting LaTeX number for you instead of typing the numbers by hand.