# Numbering of Theorem and Definitions on LaTeX

I'm currently trying to make the final amendments to a paper I've written and wondered if anyone could help.

I have a theorem and a number of definitions in a section (Section 4, for reference) and I want them labelled as :
Theorem 4.1,
Definition 4.2,
Definition 4.3, etc.

The issue is that it currently says Theorem 4.1 and then Definition 4.1, Definition 4.2 etc. How do I get it so that the labels are as stated above? i.e so that the Definition recognises the numbering of the previous Theorem?

I currently have

\documentclass[11pt, a4 paper]{article}
\usepackage[utf8]{inputenc}
\usepackage{geometry}
\geometry{a4 paper, total={170mm, 257mm}, left=20mm, top=20mm,}
\usepackage{amsthm}
\usepackage{textcomp}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{tipa}
\usepackage{graphicx}
\usepackage{enumerate}
\usepackage{ dsfont }
\graphicspath{{Images/}}
\newtheorem{theorem}{Theorem}[section]
\theoremstyle{definition}
\newtheorem{definition}{Definition}[section]
\usepackage{soul}

\tolerance=1
\emergencystretch=\maxdimen
\hyphenpenalty=10000

\begin{document}
\maketitle
\section{Section 4}
\begin{theorem} Theorem \end{theorem}
\begin{definition} Definition \end{definition}
\begin{definition} Definition \end{definition}
\end{document}


I have tried to use \newtheorem{definition}[theorem]{definition}, as I read that this would fix the problem but instead it creates a new page at the start of my project that has "[theorem]definition" on it, and the rest of the page is blank.

Any advice or help would be greatly appreciated!!

• Welcome to TeX.SE. Do you have \usepackage{amsthm} as well? As far as I know the \newtheorem{}[]{} way is introduced by amsthm (and later by other packages as well) – user31729 Mar 11 '17 at 18:28
• yes, I have it included. Sorry, I must have forgotten to include it in my original question but have added it now. – AKCJ Mar 11 '17 at 18:32
• And does it work then? – user31729 Mar 11 '17 at 18:32
• no it's still the same thing i'm afraid – AKCJ Mar 11 '17 at 18:34
• Well, we have a rule here: Show compilable codes, not just fragments only ;-) – user31729 Mar 11 '17 at 18:35

As mentioned by @Christian Hupfer, try this code (I removed the \maketitle command since your code has no \title command):

\documentclass[11pt, a4paper]{article}
\usepackage[utf8]{inputenc}
\usepackage{geometry}
\geometry{a4paper, total={170mm, 257mm}, left=20mm, top=20mm,}
\usepackage{amsthm}
\usepackage{textcomp}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{tipa}
\usepackage{graphicx}
\usepackage{enumerate}
\usepackage{dsfont}
\graphicspath{{Images/}}
\newtheorem{theorem}{Theorem}[section]
\theoremstyle{definition}
\newtheorem{definition}[theorem]{Definition}
\usepackage{soul}

\tolerance=1
\emergencystretch=\maxdimen
\hyphenpenalty=10000

\begin{document}

\setcounter{section}{3}
\section{Section 4}
\begin{theorem} Theorem. \end{theorem}
\begin{definition} A first definition. \end{definition}
\begin{definition} A second definition. \end{definition}
\begin{theorem} Another theorem. \end{theorem}

\end{document}


• thank you, this was really helpful and sorted my issues! – AKCJ Mar 12 '17 at 13:02

Here's the way with establishing a group of coupled counters with xassoccnt, i.e. theorem, definition and lemma (just added that to show that it works for more than two counters) are coupled to form a group. If one of those counters is stepped, the other ones are increased as well in order to provide the same base.

\documentclass[11pt, a4 paper]{article}
\usepackage[utf8]{inputenc}
\usepackage{geometry}
\geometry{a4paper, total={170mm, 257mm}, left=20mm, top=20mm,}
\usepackage{amsthm}
\usepackage{textcomp}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{tipa}
\usepackage{graphicx}
\usepackage{enumerate}
\usepackage{dsfont}
\usepackage{xassoccnt}
\graphicspath{{Images/}}
\newtheorem{theorem}{Theorem}[section]
\theoremstyle{definition}

\newtheorem{definition}{Definition}[section]

\newtheorem{lemma}{Lemma}[section]

\DeclareCoupledCountersGroup{theorems}
\DeclareCoupledCounters[name=theorems]{theorem,definition,lemma}
\usepackage{soul}

%\tolerance=1
%\emergencystretch=\maxdimen
%\hyphenpenalty=10000