When @code{zmacs-regions} is non-@code{nil} (this is the default), the
concept of an @dfn{active region} exists. The region is active when the
corresponding mark is active. Note that only one active region at a
-time can exist -- i.e. only one buffer's region is active at a time.
+time can exist---i.e. only one buffer's region is active at a time.
@xref{The Mark}, for more information about active regions.
@defopt zmacs-regions