The minor modes determine whether or not certain actions take place. For example, when abbrev mode is on, abbrevs are automatically expanded when typed into a buffer. Buffers may possess any number of minor modes.
(emacs) A particular characteristic which can be independently toggled on or off. For example, auto-fill mode for easing the creation of document text.
A minor mode is an optional feature of Emacs which can be switched on or off independently of all other features. Each minor mode has a command to turn it on or off. See section AD.1 Minor Modes.
A minor mode is an optional feature of Emacs which can be switched on or off independent of the major mode. Each minor mode has a command to turn it on or off. See section 27.1 Minor Modes.