Code Snippet: Theorems, Etc. in LaTeX Posted: November 16, 2020 Summary A code snippet for theorems, corollaries, lemmas, definitions, and remarks in LaTeX. Setup Put these two things in your preamble. We use the amsthm package. \usepackage{amsthm} The following sets up the styling and formatting of the environments. % To create a custom style % \newtheoremstyle{customname}{3pt}{3pt}{bodyfont}{indentamt}{headfont}{headpunct}{headspace}{headspec} \theoremstyle{plain} \newtheorem{theorem}{Theorem} \theoremstyle{plain} \newtheorem{corollary}{Corollary}[theorem] \theoremstyle{plain} \newtheorem{lemma}[theorem]{Lemma} \theoremstyle{definition} \newtheorem{definition}{Definition} \theoremstyle{remark} \newtheorem*{remark}{Remark} % To change the QED symbol to filled. % \renewcommand\qedsymbol{$\blacksquare$} Usage \begin{theorem} Theorem here... \begin{proof} Proof of theorem here... \end{proof} \end{theorem} \begin{corollary} Corollary here... \end{corollary} \begin{remark} Remark here... \end{remark} \begin{lemma} Lemma here... \end{lemma} \begin{definition}[Optional title.] Definition here... \end{definition}