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When I use \begin{lemma} .. \end{lemma} I should write \normalfont after \begin{lemma} to get normal font. Otherwise, content in lemma would be in italic font.

It is not comfortable to write \normalfont always. Is there any simpler way to make everything in lemma (and other places) in normal font with out writing this \normalfont?

\documentclass[12pt,reqno,a4paper]{amsart}
\usepackage{extsizes}
\usepackage{blindtext}
\textheight 9.3in \textwidth 6.5in
\calclayout
\usepackage{mathtools}
\usepackage{amsmath,amsthm,amsfonts,amssymb}
\newtheorem{theorem}{Theorem}[section]
\newtheorem{construction}{Construction}[section]
\newtheorem{corollary}{Corollary}[section]
\usepackage{hyperref}
\usepackage{mathrsfs}
\usepackage[all]{xy}
\usepackage[normalem]{ulem}
\newtheorem{lemma}{Lemma}[section]
\newtheorem*{question}{Question}
\theoremstyle{definition}
\newtheorem*{solution}{Solution}
\newtheorem{definition}{Definition}[section]
\newtheorem{remark}{Remark}[section]
\newtheorem{proposition}{Proposition}[section]
\newtheorem{exercise}{Exercise} 
\newtheorem{example}{Example}[section]
\usepackage{tikz-cd}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
% \renewcommand{\baselinestretch}{2} 
\usepackage{color}
\pagestyle{myheadings}
\begin{document}
\end{document}
  • The standard document classes don't define lemma, so you must have loaded a package that defines it or defined it yourself. Can you tell us how you defined lemma? It should be possible to alter the definition such that the font is not switched to italics in the first place. – moewe Jun 22 at 10:49
  • @moewe Please see edited file. I have added how I defined lemma – Praphulla Koushik Jun 22 at 10:56
  • 1
    Unrelated note: You should load hyperref at the end of your preamble, there are a few packages which should be loaded afterwards (e.g. cleveref), but as a general rule of thumb this holds true. – Skillmon Jun 22 at 11:06
  • @Skillmon Thanks.. I did not knew how that affect the outcome. Please consider to write this in your answer :) – Praphulla Koushik Jun 22 at 11:08
3

You can set the \theoremstyle prior to \newtheorem{lemma}{Lemma}{section} to definition which is a predefined style of amsthm that uses the non-italic Roman font (every \newtheorem after \theoremstyle will use that style, you can switch back to the italic style with \theoremstyle{plain}):

\documentclass[12pt,reqno,a4paper]{amsart}
\usepackage{extsizes}
\usepackage{blindtext}
\textheight 9.3in \textwidth 6.5in
\calclayout
\usepackage{mathtools}
\usepackage{amsmath,amsthm,amsfonts,amssymb}
\newtheorem{theorem}{Theorem}[section]
\newtheorem{construction}{Construction}[section]
\newtheorem{corollary}{Corollary}[section]
\usepackage{hyperref}
\usepackage{mathrsfs}
\usepackage[all]{xy}
\usepackage[normalem]{ulem}
\newtheorem*{question}{Question}
\theoremstyle{definition}
\newtheorem*{solution}{Solution}
\newtheorem{definition}{Definition}[section]
\newtheorem{remark}{Remark}[section]
\newtheorem{proposition}{Proposition}[section]
\newtheorem{exercise}{Exercise} 
\newtheorem{example}{Example}[section]
\usepackage{tikz-cd}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
% \renewcommand{\baselinestretch}{2} 
\usepackage{color}
\pagestyle{myheadings}
\theoremstyle{definition}
\newtheorem{lemma}{Lemma}[section]
\begin{document}
\begin{lemma}
  This is a lemma
\end{lemma}
\begin{theorem}
  This is a theorem
\end{theorem}
\end{document}

enter image description here

  • So, you are saying if I write \theoremstyle{definition} before every \newtheorem I define, everything will be in normal font.. Is that correct? – Praphulla Koushik Jun 22 at 11:01
  • @PraphullaKoushik \theoremstyle acts as a switch, every \newtheorem after \theoremstyle will use that style, amsthm comes with 3 predefined styles, plain, definition, remark, plain is the default one, definition is similar but uses an upright font, remark uses an upright font and less vertical spacing around it. – Skillmon Jun 22 at 11:04
  • I am slightly confused.. You are saying plain is the default one so, it should give non italic font right? wHat am I missing :O – Praphulla Koushik Jun 22 at 11:09
  • @PraphullaKoushik As it turns out plain isn't actually plain in the usual sense of the word here. Have a look at §4.1 The \theoremstyle command of the amsthm documentation (amsthdoc), which explains that plain means "italic text, extra space above and below". – moewe Jun 22 at 11:24
  • @moewe Oh Ok Ok :) Thank you :) I will read – Praphulla Koushik Jun 22 at 11:25

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