General ⇒ Command \def already defined (newtheorem)

[Plato]

Code: Select all

%Preamble
\documentclass[11pt,a4paper]{article}
\usepackage{amssymb,amsmath,amsthm}
\usepackage[dutch]{babel}
\setlength{\parindent}{0cm}
\setlength{\parskip}{0cm}
\theoremstyle{definition}
\newtheorem{def}{Definitie}
\begin{document}
\begin{titlepage}

Hey guys, I am writing about lineair algebra and of course I wish to use definitions, theorems, corollaries, lemmas, remarks etc.
I'm kind of new to LaTeX, and every time I command LaTeX to create automatical definitions for me, I get the error:

"! LaTeX Error: Command \def already defined.
or name \end... illegal, see p. 192 of the manual."

I don't know what I'm doing wrong, I use the commands:
\begin{def}
...
\end{def}

I've tried to remove amssymb and amsmath from the packages (and only keeping amsthm) but that doesn't fix it either.

Any help would be appreciated, thanks in advance.

[Johannes_B]

Hi and welcome,

\def is an internal primitive and used in many many many instances. It defines new macros.

Use another word to call your definitions, like dfn or defi or defn or ... Or write the complete word, a good editor can help you in saving typing time.

[Dyexz]

you could try something like:

Code: Select all

\usepackage{amssymb,amsmath,amsthm}
\usepackage[dutch]{babel}
\setlength{\parindent}{0cm}
\setlength{\parskip}{0cm}
\theoremstyle{break}           % "break" style makes a linebreak after the header of "Definition X.X"
\newtheorem{defn}[]{Definitie} % you can put chapter or section into the [] to define how the definitions are numbered
\newenvironment{definition}{\begin{defn}}{\end{defn}}  % this creates an environment where you use the commands \begin{defn} \end{defn} when creating a definition

[Plato]

Thanks both, that fixed it.