# How do I add \begin{definition} … \end{definition}?

I have the following preamble:

\documentclass{article}
\usepackage{graphicx}
\usepackage{hyperref}
\usepackage{amssymb}
\usepackage{amsthm}
\usepackage{yfonts}
\usepackage[inline]{enumitem}

\newcommand{\subscript}[2]{$#1 _ #2$}

\newtheorem{theorem}{Theorem}

\title{Jumbo}

\author{Frode Alfson Bj\o{}rdal}
\date{}

\begin{document}


How can I get \begin{definition} … \end {definition} here?

• See how you defined theorem. Also you might want to have a look in the amsthm manual to familiarize yourself with the \newtheorem syntax. – daleif Aug 10 '17 at 8:28
• Also note that your example has no chance to work as \institute and \email is not defined in the article class – daleif Aug 10 '17 at 8:29
• In reality I have %\institute{Affiliation Institute \at Collegium Anonymia \\\email{clancularius@collegium.com}}, and so I delete this from my MWE. – Sapiens Aug 10 '17 at 11:19

Just define it using \newtheorem like you have done for environment theorem:

\documentclass{article}
\usepackage{amsthm}
\newtheorem{definition}{Definition}
\begin{document}
\begin{definition}
This is a definition.
\end{definition}
\end{document}


For more information about \newtheorem and how to use another style for the new theorem environment definition, e.g., using \theoremstyle{definition} before \newtheorem, see the manual of package amsthm.

• if upright text is wanted (more usual for a definition), precede the \newtheorem{definition} by \theoremstyle{definition}. (defined by amsthm.) – barbara beeton Aug 10 '17 at 19:46