Quoting Kopka and Daly, Guide to LaTeX, p. 54:
\twocolumn[<header text>]
Terminates the current page, starting a new one with two columns per
page. The optional header text is written at the top of the page in
one column with the width of the whole page.
[...]
The [standard class] option twocolumn
automatically changes certain
page style parameters, such as indentation, compared with the
one-column format. This does not occur with the command \twocolumn
.
These additional changes must be made with the corresponding
\setlength
declarations if they are desired. If the bulk of the
document is in two-column format, the class option is to be preferred.
Note that the argument of \chapter
will also span the width of the whole page in twocolumn
mode. Using \chapter
inside the optional argument of \twocolumn
will produce an error (Float(s) lost
).
EDIT: According to the UK TeX FAQ, there is at least one case in standard LaTeX where manually switching to @twocolumnfalse
is useful: One-column abstracts in a two-column article
. Try to comment out \begin{@twocolumnfalse}
and \end{@twocolumnfalse}
in the following example:
\documentclass{article}
\newcommand*{\sometext}{Lorem ipsum dolor sit amet, consectetuer
adipiscing elit. Ut purus elit, vestibulum ut, placerat ac,
adipiscing vitae, felis. Curabitur dictum gravida mauris.}
\begin{document}
\twocolumn[
\begin{@twocolumnfalse}
\begin{abstract}
\sometext
\end{abstract}
\end{@twocolumnfalse}
]
\sometext
\end{document}
@twocolumnfalse
isn't necessary to write about the whole line. It's the default behaviour of\twocolumn[]
. – Marco Daniel May 28 '12 at 8:49