Common LaTeX Errors and How to Fix Them

! Missing $ inserted.
<inserted text>
                $
l.15 The area is x^
                    2 square units.

! Missing $ inserted.
<inserted text>
                $
l.10 The formula x^2 + y^2 = z^
                                2 shows...

The formula x^2 + y^2 = z^2 shows the Pythagorean theorem.
The value is approximately \pi.

The formula $x^2 + y^2 = z^2$ shows the Pythagorean theorem.
The value is approximately $\pi$.

! Undefined control sequence.
l.12 \begn
          {document}

% Wrong
\begn{document}
\sectoin{Title}
\includ{file}

% Correct
\begin{document}
\section{Title}
\include{file}

% Wrong - using \includegraphics without graphicx
\documentclass{article}
\begin{document}
\includegraphics{image}  % Error!
\end{document}

% Correct - add the package
\documentclass{article}
\usepackage{graphicx}
\begin{document}
\includegraphics{image}
\end{document}

! Missing } inserted.
<inserted text>
                }
l.8 \textbf{This is bold text

\textbf{This is bold text

\section{Introduction

\textit{Nested \textbf{formatting} example

\textbf{This is bold text}

\section{Introduction}

\textit{Nested \textbf{formatting} example}

% Use editor brace matching (hover over { to find matching })
\textbf{This is \textit{nested} text}
       ^                            ^
       |____________________________|

! LaTeX Error: File `myimage.png' not found.

Type X to quit or <RETURN> to proceed,
or enter new name. (Default extension: png)

% If your file structure is:
% project/
%   main.tex
%   images/
%     diagram.png

% Wrong
\includegraphics{diagram}

% Correct
\includegraphics{images/diagram}

% File is named "Diagram.png"

% Wrong (on Linux/Mac)
\includegraphics{diagram}

% Correct
\includegraphics{Diagram}

% Wrong
\bibliography{References}  % But file is references.bib

% Correct
\bibliography{references}

! LaTeX Error: Environment align undefined.

% Wrong
\begin{itemise}
\end{itemise}

% Correct
\begin{itemize}
\end{itemize}

% Wrong - align needs amsmath
\documentclass{article}
\begin{document}
\begin{align}
    y &= mx + b
\end{align}
\end{document}

% Correct
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align}
    y &= mx + b
\end{align}
\end{document}

Overfull \hbox (15.2pt too wide) in paragraph at lines 10--12
Underfull \hbox (badness 10000) in paragraph at lines 15--17

% Option 1: Allow hyphenation
\usepackage[hyphens]{url}

% Option 2: Use sloppypar for problematic paragraphs
\begin{sloppypar}
This paragraph contains a very long URL or technical term
that LaTeX struggles to break properly.
\end{sloppypar}

% Option 3: Add manual break hints
super\-cali\-fragi\-listic

% Option 4: For URLs
\usepackage{hyperref}
\url{https://very-long-url-that-causes-problems.com/path}

% Usually happens with \\ at paragraph end
% Wrong
This is the end of a paragraph.\\

% Correct
This is the end of a paragraph.

! LaTeX Error: Missing \begin{document}.

% Wrong
\documentclass{article}
\usepackage{amsmath}
This text is in the wrong place!  % Error here
\begin{document}
Actual content
\end{document}

% Correct
\documentclass{article}
\usepackage{amsmath}
\begin{document}
This text is in the right place!
Actual content
\end{document}

% Sometimes copy-paste introduces hidden characters
% Delete and retype the line if you suspect this
\documentclass{article}  % Delete and retype this line
\begin{document}
\end{document}

! Too many }'s.
l.15 }

% Wrong
\textbf{Some bold text}}

% Correct
\textbf{Some bold text}

% Wrong
\begin{itemize}
    \item First
\end{enumerate}  % Wrong environment!

% Correct
\begin{itemize}
    \item First
\end{itemize}

! Misplaced alignment tab character &.
l.10 Bread & butter

% Wrong
Bread & butter
Smith & Jones LLC

% Correct
Bread \& butter
Smith \& Jones LLC

% Wrong - 3 columns defined, but 4 values in row
\begin{tabular}{|l|c|r|}
    A & B & C & D \\  % Error! Too many &
\end{tabular}

% Correct
\begin{tabular}{|l|c|r|l|}  % 4 columns
    A & B & C & D \\
\end{tabular}

! Dimension too large.
l.25 \includegraphics[width=2\textwidth]{image}

% Wrong
\includegraphics[width=2\textwidth]{image}

% Correct
\includegraphics[width=\textwidth]{image}
\includegraphics[width=0.8\textwidth]{image}

% Wrong - this creates infinite stretch
\hspace{\fill}text\hspace{\fill}

% Correct
\hfill text \hfill

% Comment out half your document
\begin{document}
First half of content
%{
Second half of content
%}
\end{document}

% Create minimal example
\documentclass{article}
\begin{document}
% Paste suspicious code here
\end{document}

This is pdfTeX, Version 3.141592653
...
! Missing $ inserted.
<inserted text>
                $
l.10 x^
      2

# Delete auxiliary files and recompile
rm *.aux *.log *.toc *.out