Mode has several meanings:

• In statistics, the mode is the value that has the largest number of observations, namely the most frequent value or values. See mode (statistics).
  • In particular, in fashion, the mode is the trend followed by the largest number of people.
• In music a mode is a kind of scale; see musical mode.
• In complex systems, in general, a mode is a specific type of operation: for example in a military avionics system, a fighter plane radar might be in track mode or scan mode or track while scan mode, with distinctly different behavior and intention.
• In computer software, a mode is distinct method of operation within a computer program, in which the same user input can produce different results depending of the state of the computer. See also modeless, quasimode. Three popular examples of software employing modes:
  • vi - has one mode for inserting text, and a separate mode for entering commands. Some people also call vi's ability to line-edit a "mode" (even though it is launched outside of vi's normal interface, by invoking "ex" from the operating system's command line interface.)
  • Emacs - has many modes that can be evoked based on file type to more easily edit files of a certain type. Modes are written in Emacs's LISP, and all modes may not be included with all versions.
  • CIOS (Cisco Internetworking Operating System) - in order to gain the privilege to execute certain commands, you must enter a certain mode that allows you to execute that command.
  • Also, tool palettes in photo-editing and drawing applications are classical examples of a modal interface.

• In computer file systems, a common element of metadata in a file is the mode, which is usually understood to mean the type of the file and the set of permissions it has. See stat (Unix).

• In a waveguide or cavity the mode is one of the possible patterns of electromagnetic field. Available patterns are derived from Maxwell's equations and the applicable boundary conditions. They may be longitudinal or transverse.
  • An example of waveguide mode: fiber optic mode.
  • An example of cavity mode: laser mode.

• In acoustics, a mode is one of the possible patterns of vibration, analogous to waveguide and cavity modes, only that electrical and magnetical fields are replaced by velocity and displacement. Each mode has a characteristic vibrational frequency and damping. See also: Ernst Chladni, Cymatics.
  • An example of acoustic modes: An "ideal" guitar string of length L, fixed at both ends, will have modes in the shape of sin(n*x*pi/L), where n is the mode number.

See also modality.