How to control the space around items in enumerated list globally

Question

The second fully voted answer of ths question suggest that to use \itemsep0em for reduce the spaces between items locally. But how can I define it to be implemented for whole the document and for just the enumerate list. Here is my code sample:

 \documentclass[]{article}
 \usepackage{enumitem}
 \begin{document}
 \begin{enumerate}
            \item[a] $f=x^2-3y^2-8x+9y+3xy$
            \item[b] $f=x^2+4y^2-6x+16y$
            \item[c]$f=xy-x+y$
            \item[d] $f=\dfrac{5x^3}{3}+\dfrac{2}{3}y^3-\dfrac{15}{2}x^2+y^2-4y+7$
 \end{enumerate}
 \end{document}

and I want to set a certain value for the space between items globally. Should it be like the following cod:

\AtBeginEnvironment{enumerate}{\itemsep}{0pt}

Sorry if the above code makes you annoyed. 😞

Thanks for your time! 🙏🙏

Answer 1

You can also define a new environment:

\documentclass{article}

\newenvironment{my_enumerate}{
\begin{enumerate}
  \setlength{\itemsep}{0pt}
  \setlength{\parskip}{0pt}
}{\end{enumerate}}

\begin{document}
\begin{my_enumerate}
    \item[a] $f=x^2-3y^2-8x+9y+3xy$
    \item[b] $f=x^2+4y^2-6x+16y$
    \item[c] $f=xy-x+y$
    \item[d] $f=\frac{5x^3}{3}+\frac{2}{3}y^3-\frac{15}{2}x^2+y^2-4y+7$
\end{my_enumerate}
\end{document}

If you need them even closer, you can use negative numbers, but be careful not to cause overlapping text.