Why is the word "modal" used to describe forms?

Question

We all know what "modal" forms are in windowed programming environments: forms that must be closed before the rest of the application GUI can be accessed again.

Why is the word "modal" used to describe this concept?

Answer 1

I believe it's because you're in a specific mode that you can't escape from until you dismiss the dialog box or form.

Normal modal dialog boxes meant you couldn't do anything else in that application. System modal was defined as "cannot do anything else with the system at all" until you're finished.

Answer 2

Wikipedia is useful on this one, as it gives Jef Raskin's definition of 'Mode':

"An human-machine interface is modal with respect to a given gesture when (1) the current state of the interface is not the user's locus of attention and (2) the interface will execute one among several different responses to the gesture, depending on the system's current state."

http://en.wikipedia.org/wiki/Mode_(computer_interface)

A Modal form is one that has enacts a different 'mode' from the rest of the application.