Why is this code giving me an Overfull \hbox error?

Question

I am getting an Overfull \hbox error and I've managed to trim the original big complicated file to this simple source that shows the problem:

\documentclass{article}
\begin{document}
\parindent=0pt
changed systematically, and the intensity that manages to survive passage through
\end{document}

When I compile this using pdflatex myfile.tex I get:

Overfull \hbox (6.77846pt too wide) in paragraph at lines 5--6
[]\OT1/cmr/m/n/10 changed sys-tem-at-i-cally, and the in-ten-sity that man-ages
 to sur-vive pas-sage through

I've tried it with both MikTex and TexLive and I get the same error on both. I cannot understand what is going on. Why doesn't Latex break the line before the word "through" instead of overflowing the right margin and reporting an error, and how can I fix this?

I did a default install on Windows 10 and MikTex has picked up the regional settings and set the paper size to A4. I mention this because presumably a different paper size would change the line length and probably change the output. If it is relevant the MikTex settings look like this:

In this paragraph TeX doesn't succeed to format text as desired, consequently this text line protrude out of text border. Usually the cause is part of text, which can not be hyphenated (like boxes or part in-kine equations). Such warning disappear if you enable ragged right side of text or rephrase text accordingly. Also use of microtype package may help. — Zarko, Feb 03 '22 at 11:31
@Zarko but why doesn't it simply split the input before the word through and flow the text onto two lines? — John Rennie, Feb 03 '22 at 11:33
You can also use \sloppy or sloppy par to give TeX a bit more freedom. — Pieter van Oostrum, Feb 03 '22 at 11:34
Words can be split according to hyphenation patterns (depended from used languages, defined by babel Of course you can do this manually, but people do this only if there is no defined pattern for particular word. — Zarko, Feb 03 '22 at 11:36
If you start the sentence with the capital "C", it will make a correct typeset without the warning. Whether is it a bug or intentional behaviour, I don't know. — Celdor, Feb 03 '22 at 11:37
@Celdor I think that just changes the length when typeset. I also found that inserting extra random words fixed the problem, but again I think this is just changing the length when typeset. — John Rennie, Feb 03 '22 at 11:40
General question → boxes - What does "overfull hbox" mean? (Why is there a black mark at the end of a line?) - TeX - LaTeX Stack Exchange || this particular question is pretty close to boxes - What is a "Overfull \hbox (9.89561pt too wide)"? - TeX - LaTeX Stack Exchange // (same reason, but it happens much more rarely with English for obvious reason) // same fix (sloppypar) works. — user202729, Feb 03 '22 at 11:56

score 2 · Answer 1 · answered Feb 03 '22 at 12:35

User202729 has answered this in a comment, but given that comments are potentially ephemeral I will post it as an answer.

When LaTeX is justifying text it will not let the white space between words expand too much. Where a line contains a few long words, justifying the text might require the spaces between the words to be increased to a point where they look odd. If this happens LaTeX will instead let the line overflow the right margin and this generates the overfull hbox error.

The easy fix is to bracket the offending paragraph between:

\begin{sloppypar}

and

\end{sloppypar}

as this specifies that the spaces between words can be expanded as necessary to justify the text.

score 1 · Accepted Answer · answered Feb 03 '22 at 13:34

Leave solving overfull lines for the very last phase of document production, because even minimal changes to the text might solve the issue.

You have several strategies available, the main one is rewording. Nobody is like Mozart who allegedly was able to write down a complete piece with orchestration and all in a single work session: reread your paragraphs and quite likely you'll find some weak point or, at least, different wording to express the same thing without the paragraph being badly typeset.

Remove or add an adjective; place a missing comma, remove one too much; add a tie ~ to keep some words together. There are many other possibilities.

If all else fails, there are other tools available without resorting to the ultimate weapon sloppypar. I find it convenient to locally set \emergencystretch without touching \tolerance like sloppypar does. Here's a comparison.

\documentclass{article}
\begin{document}
\parindent=0pt

overfull

\medskip
changed systematically, and the intensity that manages to survive passage through
changed systematically, and the intensity that manages to survive passage through
changed systematically, and the intensity that manages to survive passage through
\bigskip

not overfull

\medskip
changed systematically, and the intensity that manages to survive passage through
changed systematically, and the intensity that manages to survive passage through
changed systematically, and the intensity that manages to survive passage through
{\setlength{\emergencystretch}{0.5\textwidth}\par}
\bigskip

sloppy

\medskip
\begin{sloppypar}
changed systematically, and the intensity that manages to survive passage through
changed systematically, and the intensity that manages to survive passage through
changed systematically, and the intensity that manages to survive passage through
\end{sloppypar}
\end{document}

The trick I used is to issue \par in a group where \emergencystretch is set to a nonzero value. The } brace after \par ensures that this setting won't carry over for the rest of the document.

You can see that my trick better distributes badness across all lines, rather than concentrate it in the first line like in the sloppypar case.

Take your time to solve each overfull and your document will look perfect. But I emphasize once again that rewording is the best approach in the vast majority of cases.

Why is this code giving me an Overfull \hbox error?

2 Answers2