Common Errors

How to Fix 'Undefined Control Sequence' Error in LaTeX

'Undefined control sequence' is the most common LaTeX error. It means LaTeX found a command (\something) that it doesn't recognize.

Common Causes

The most frequent causes of this error:

% 1. Typo in command name
\textbf{bold}    % Correct
\textbolf{bold}  % Wrong - typo!

% 2. Missing package
\includegraphics{}  % Error without graphicx package
\usepackage{graphicx}  % Add this to fix

% 3. Wrong command
\bold{text}    % Wrong
\textbf{text}  % Correct

Reading the Error

LaTeX tells you exactly which command failed:

! Undefined control sequence.
l.42 \textbolf
              {my text}
% The error is on line 42, command is \textbolf

Common Fixes

Quick solutions for frequent errors:

% For images:
\usepackage{graphicx}

% For URLs:
\usepackage{hyperref}

% For colors:
\usepackage{xcolor}

% For math (align, etc):
\usepackage{amsmath}

💡 Tips

•Google the exact command name - you'll find which package provides it
•Check spelling carefully - LaTeX is case-sensitive
•Look at the line number in the error message

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