How to change the way theorems are numbered

I am trying to write a small note in which there are no sections, and the theorems go from 1,2,3. In the following code, for example:

\documentclass[12pt]{article}
\newtheorem{theorem}{Theorem}[section]
\newtheorem{definition}[theorem]{Definition}
\newtheorem{remark}[theorem]{Remark}
\title{Some Notes}
\begin{document}
\date{}
\maketitle
\begin{definition}
A group is defined as ...
\end{definition}
\begin{remark}
The concept of groups...
\end{remark}
\end{document}


I get Definition 0.1. However I want only Definition 1 to be printed instead. Furthermore I want Remark 1, instead of Remark 0.2.

How can I accomplish this?

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Just remove [section] and do \newtheorem{theorem}{Theorem}. – egreg Aug 18 '14 at 9:22

When you do

\newtheorem{theorem}{Theorem}[section]


you're telling LaTeX that theorem environments should be numbered as

<section number>.<theorem number>

and that the theorem number must be reset when a new section comes along.

The [section] part is optional, as the syntax suggests, so you just have to do

\newtheorem{theorem}{Theorem}


Full example:

\documentclass[12pt]{article}
\newtheorem{theorem}{Theorem}
\newtheorem{definition}[theorem]{Definition}
\newtheorem{remark}[theorem]{Remark}

\begin{document}

\title{Some Notes}
\author{Me}
\date{}
\maketitle

\begin{definition}
A group is defined as ...
\end{definition}

\begin{remark}
The concept of groups...
\end{remark}

\begin{theorem}
Groups are fun.
\end{theorem}

\end{document}


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If there is no section used, the section counter is 0, therefore the theorem enviroment prints 0.1 etc.

Since the OP has the remark as a sibling of theorem environment, it will just increment the theorem counter and the number of the 1st remark will be 0.2, not 1.

If \thetheorem and \theremark commands are redefined such that the section counter value information is removed, the output will be as desired.

\documentclass[12pt]{article}
\newtheorem{theorem}{Theorem}[section]
\newtheorem{definition}[theorem]{Definition}
\newtheorem{remark}{Remark}[theorem]

\renewcommand{\theremark}{\arabic{theorem}}

\renewcommand{\thetheorem}{\arabic{theorem}}

\title{Some Notes}
\begin{document}
\date{}
\maketitle
\begin{definition}\label{def::1}
A group is defined as ...
\end{definition}
\begin{remark} \label{remark::1}
The concept of groups...
\end{remark}

\begin{definition}
Well....
see \ref{remark::1} as well
\end{definition}
\begin{remark}
In \ref{def::1} you saw%
\end{remark}

\end{document}


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