Is \def sensitive to spacing?

Is \def sensitive to spacing?

In the code below, it took me a long time to figure out that the space in
the second line below beginning with \def generates an error.
I'm new here. Where is the documentation of \def that would help me
understand this issue? Stanley Ocken
\documentclass[aspectratio=1610]{beamer}
\begin{document}
\def\funa(#1,#2){ (#2)*(#1)^2} % OK
%\def\funa(#1,#2) { (#2)*(#1)^2 } % NOT OK ...WHY?
\begin{frame}
\pgfmathparse {\funa(3,4)} \pgfmathresult \\
\end{frame}
\end{document}-