Common Errors

How to Fix 'Missing $ Inserted' Error in LaTeX

The 'Missing $ inserted' error means you used a math-only symbol outside of math mode. LaTeX requires special delimiters for mathematical notation.

Understanding the Error

Some characters only work in math mode:

% ERROR - underscore outside math mode:
x_1 is a variable

% FIXED - wrap in $:
$x_1$ is a variable

% ERROR - superscript outside math mode:
E = mc^2

% FIXED:
$E = mc^2$

Math Mode Delimiters

Different ways to enter math mode:

% Inline math:
$x^2 + y^2 = z^2$
\(x^2 + y^2 = z^2\)

% Display math (centered, own line):
$$E = mc^2$$
\[E = mc^2\]

% Numbered equation:
\begin{equation}
  E = mc^2
\end{equation}

Common Math Symbols

These ALWAYS need math mode:

$ _ ^  % subscript, superscript
$\alpha \beta$  % Greek letters
$\sum \int$     % operators
$\frac{a}{b}$   % fractions
$\sqrt{x}$      % roots

💡 Tips

•If you want a literal underscore in text, use \_
•For chemical formulas like H₂O, use: H\textsubscript{2}O
•Greek letters only work in math mode

Try This in Bibby AI

Write LaTeX faster with AI auto-complete and instant compilation.

Start Writing Free