Math Command Missing An Argument

A math command was used with fewer arguments than it takes (\frac{a} has one, needs two), or a macro was called with the wrong number of arguments.

Q-22-4 — Math Command Missing An Argument

A math command was used with fewer arguments than it takes (\frac{a} has one, needs two), or a macro was called with the wrong number of arguments.

What this means

Commands such as \frac, \sqrt, \overset and \binom take a fixed number of brace-delimited arguments, and a macro takes the number declared in its \newcommand. When an argument is missing, the command is emitted as an error at its position and the equation falls back to verbatim source in formats that need a conversion.

Why this happens

Common causes: an unfinished edit (\frac{a} with the denominator still to write), a brace typed as a parenthesis (\frac(a)(b)), or a macro used with the wrong count (\newcommand{\pr}[2]{…} \pr{x}).

How to fix it

Supply every argument in braces. Single characters may be given bare (\frac12), but anything longer needs {…}.

Where it is reported

Math diagnostics point into the .qmd at the exact characters inside the $…$ or $$…$$ block, including math that spans several lines or sits inside a block quote or list item. When a \newcommand macro is involved, a problem inside the macro body points at the definition and a problem in a macro argument points at the use.