A dialog box that blocks further work being done in the application until it is dismissed.

This is a dialog box, or window, that must be responded to before operation of a program can continue. Modal dialog boxes are easier to program than modeless dialog boxes since you don't have to account for as many conditions. However, modal dialog boxes are generally annoying to users. Common examples are errors (file not found) and "are you sure" questions.

a dialog (message box, for instance) that blocks the application that popped it until the dialog is closed (answered or dismissed)

a dialog presented by the user interface that asks the user to make a decision before carrying out any other actions, such as invoking an application or opening a document

a dialog that blocks input to other visible windows in the same application

a dialog that is displayed and blocks the application until the user has finished answering the questions posed in the dialog

a dialog which will block any interaction with any other window of the program except for the indicated dialog window, until the modal event loop is exited

a window that pops up and requires attention, and will not let the user communicate with the main window while it operates

In AIXwindows, a Dialog widget that interrupts the work session to solicit input from the user.