It /makes/ an environment. That's entirely different.
% typeset regardless of the current mode setting.
%
% \DescribeMacro\newslowboxenv
% typeset regardless of the current mode setting.
%
% \DescribeMacro\newslowboxenv
-% There's an environment for building slow box environments. Say
+% There's a command for building slow box environments. Say
% \syntax{"\\newslowboxenv{"<env-name>"}"\* "["<n-args>"]"\*
% "{"<before-text>"}"\* "{"<start-text>"}"\* "{"<end-text>"}"\*
% "{"<after-text>"}"}. This creates a new environment (just like with
% \syntax{"\\newslowboxenv{"<env-name>"}"\* "["<n-args>"]"\*
% "{"<before-text>"}"\* "{"<start-text>"}"\* "{"<end-text>"}"\*
% "{"<after-text>"}"}. This creates a new environment (just like with