From Hans message on the mailing list:
<blockquote>
Another addition is that
\definemode[something][keep]
define an undefined mode; the keep makes sure that the already set value is
kept (another option is 'yes').
Using defined modes (that is, set with: \enabledmode, \disablemode or
\definemode) can be tested about twice as fast as undefined modes which can
make a small difference when modes are tested lots of times.
</blockquote>
Add to the main article with appropriate example --[[User:Adityam|Aditya]] 20:20, 27 June 2014 (CEST)