# Strange error with inputenc [closed]

The head of my document looks like

\documentclass[intlimits,twoside,a4paper]{article}

\usepackage[utf8]{inputenc}
\usepackage[eqsecnum]{cmpj3}
\usepackage{bm}

\usepackage{float}

\newcommand{\ii}{\mathrm{i}}

\articletype{Regular article}


But when I try to compile the document, it fails and writes:

Package inputenc Error: Keyboard character used is undefined(inputenc) in inputencoding utf8. \section.

The error appears for the string \section{Derivation}, but I don't understand, what is the reason for this.

Can you help?

## closed as unclear what you're asking by Bobyandbob, Stefan Pinnow, user36296, Joseph Wright♦Jun 8 '18 at 9:00

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• inputenc defines definitions for a few hundred characters and Unicode has a few thousand characters so getting this error is expected. If you had shown the full error, or shown a test document, we would know which character was undefined, and could suggest a definition. – David Carlisle Jul 19 '17 at 6:51