Undefined control sequence

TeX Output

./example.tex:3: Undefined control sequence.
l.3 This has an \undefinedcommand
                                 {here}.

Explanation

TeX encountered a command (macro starting with \) that has not been defined in the LaTeX kernel, the document class, or any loaded package.

How to Fix

1. Check for typos in the command name (e.g. \textbld instead of \textbf, or \cal instead of \mathcal).
2. If the command comes from an external package (such as \mathbb from amssymb or \href from hyperref), add \usepackage{...} to your document preamble.
3. If writing custom macros, define it using \newcommand{\mycmd}{...} before invoking it.