Minor modes each put a word on the mode line to signify that they're active. This can cause other displays, such as % of file that point is at, to run off the right side of the screen. For some minor modes, such as mouse-avoidance-mode, the display is a waste of space, since users typically set the mode in their .emacs and never change it. For other modes, such as jiggle-mode, it's a waste because there's already a visual indication of whether the mode is in effect.

A diminished mode is a minor mode that has had its mode line display diminished, usually to nothing, although diminishing to a shorter word or a single letter is also supported. This package implements diminished modes.