One of a number of parameters that may be set for Unix tool programs, each specifying special instructions (e.g, with the sort tool, sort -rn specifies everse umeric sort). Each program has its own unique array of possible switches, invoked on the command-line before arguments, using a switch prefix (normally minus sign "-") before the individual letters indicating the switch settings, thus resembling clitics on the command verb. May be set by menu or checkbox in a GUI. Also called options or preferences.
An instruction, added to a command, that designates a course of action, other than default, for the command process to follow.
A command switch is an option that a command uses to change what it's doing and how it's doing it. Most switches are specified starting with a slash (/) or a hyphen (-), followed by a single letter.