\newcommand\morf[4][\to]{#2\colon #3#1 #4} % \morf{f}{A}{B} = f\colon A\to B
\newcommand\diff[3][\partial]{\frac{#1 #2}{#1 #3}}
\newcommand\inverse{^{-1}}  % hvis man tit skal skrive ^{-1}, ie $X\inverse$
\newcommand\isomorph{\cong} % \cong anvendes ofte til dette
\newcommand\homotopyeq{\simeq} % fra topologi
\newcommand\DistAs{\sim}       % X \DistAs N(0,1)
\newcommand\ObsFromDist{\sim\sim} % observation fra variabel distribueret som...
\newcommand\DistEq{\stackrel{\smash{\scriptscriptstyle(d)}{=}}} % lighed i distribution