Indent first paragraph only once

I'm writing a document in English which includes an abstract in Spanish. In Spanish the first paragraph of a chapter should be indented, while in English shouldn't.

If I use indentfirst package, all first paragraphs in the document would be indented.

How can I indent a first paragraph only once, i.e., without affecting other first paragraphs in the document?

EDIT: I only want to indent the first line of paragraphs. \indent doesn't do the job, maybe because it's overridden to not indent first paragraphs.

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Why not use \indent? –  fefe Apr 23 '12 at 12:04
I think because he wants the whole paragraph to be indeted, not the first line only. –  Ray Apr 23 '12 at 12:16
I want to indent only the first line. \indent doesn't work, I suppose because it's overriden to not indent the first paragraph. –  Jose Apr 23 '12 at 12:33
@Jose In this case you should really edit your question accordingly since it says "How can I indent a first paragraph only once". –  Ray Apr 23 '12 at 12:40

\indent does not work as the code LaTeX inserts to remove the indentation after a section heading really does remove the indentation box, even if added explicitly.

Try

\section{hhh}
\hspace*{\parindent}aa bb ccaa

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Brilliant, thanks a lot –  Jose Apr 23 '12 at 14:54

Add to the code executed when entering Spanish what's done by indentfirst; we do also the converse, when exiting Spanish.

\documentclass{article}
\usepackage[spanish,english]{babel}
\makeatletter
\let\original@afterindentfalse\@afterindentfalse
\makeatother
\usepackage{lipsum}
\begin{document}
\begin{otherlanguage}{spanish}
\section{\abstractname}
\lipsum[2]
\end{otherlanguage}

\lipsum[3]
\end{document}

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yes +1 for me as no one else had, and this is of course the right way to do it if you have lots of spanish and english sections. If it's just a single abstract though, I thought the hspace was simpler even if it does pollute the document markup a bit. –  David Carlisle Apr 23 '12 at 15:30
@DavidCarlisle Of course: one single indent does not require a complicated solution. I'd be even more drastic: if the base language is English, follow the conventions of English. –  egreg Apr 23 '12 at 16:35

You could set up a new environment if you would like to indent a full paragraph.

\newenvironment{myindentpar}[1]
{\begin{list}{}
{\setlength{\leftmargin}{#1}}
\item[]
}
{\end{list}}


Then you could call this environment by

\begin{myindentpar}{3cm}
text text text...
\end{myindentpar}


In case you just want to indent a single line I would suggest the \indent command.

Source

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Thanks for the answer, but yes, I want to indent only the first line. \indent doesn't do the job, maybe because it's overriden to not indent the first paragraph? –  Jose Apr 23 '12 at 12:35