Here, we list the symbol properties which are used for special purposes in Emacs. In the following table, whenever we say “the named function”, that means the function whose name is the relevant symbol; similarly for “the named variable” etc.
nil, specifies the number of extra slots in the named char-table type. See Char-Tables.
deffaceand related functions. See Defining Faces.
defcustomand related functions. See Variable Definitions.
nil, the named function is disabled as a command. See Disabling Commands.
defface. See Defining Faces.
nil, specifies the maximum minibuffer history length for the named history list variable. See Minibuffer History.
interactivespecial form instead. See Interactive Call.
special, the named major mode is special. See Major Mode Conventions.
nil, the named variable is a buffer-local variable whose value should not be reset when changing major modes. See Creating Buffer-Local.
nil, the named function should not be deleted from the local value of a hook variable when changing major modes. See Setting Hooks.
nil, the named function is considered to be side-effect free. Calls with constant arguments can be evaluated at compile time. This may shift run time errors to compile time.
nil, the named variable is considered risky as a file-local variable. See File Local Variables.
nil, the named function is considered generally safe for evaluation. See Function Safety.
nil, the named function is safe to call in file-local evaluation forms. See File Local Variables.
nilvalue indicates that the named function is free of side-effects, for determining function safety (see Function Safety) as well as for byte compiler optimizations. Do not set it.
nil, this specifies the named variable's documentation string. This is set automatically by
defvarand related functions. See Defining Faces.