Standard Symbol Properties

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.

:advertised-binding: This property value specifies the preferred key binding, when showing documentation, for the named function. See Keys in Documentation.
char-table-extra-slots: The value, if non-nil, specifies the number of extra slots in the named char-table type. See Char-Tables.
customized-face
face-defface-spec
saved-face
theme-face: These properties are used to record a face’s standard, saved, customized, and themed face specs. Do not set them directly; they are managed by defface and related functions. See Defining Faces.
customized-value
saved-value
standard-value
theme-value: These properties are used to record a customizable variable’s standard value, saved value, customized-but-unsaved value, and themed values. Do not set them directly; they are managed by defcustom and related functions. See Variable Definitions.
disabled: If the value is non-nil, the named function is disabled as a command. See Disabling Commands.
face-documentation: The value stores the documentation string of the named face. This is set automatically by defface. See Defining Faces.
history-length: The value, if non-nil, specifies the maximum minibuffer history length for the named history list variable. See Minibuffer History.
interactive-form: The value is an interactive form for the named function. Normally, you should not set this directly; use the interactive special form instead. See Interactive Call.
menu-enable: The value is an expression for determining whether the named menu item should be enabled in menus. See Simple Menu Items.
mode-class: If the value is special, the named major mode is special. See Major Mode Conventions.
permanent-local: If the value is non-nil, the named variable is a buffer-local variable whose value should not be reset when changing major modes. See Creating Buffer-Local.
permanent-local-hook: If the value is non-nil, the named function should not be deleted from the local value of a hook variable when changing major modes. See Setting Hooks.
pure: If the value is non-nil, the named function is considered to be pure (see What Is a Function). Calls with constant arguments can be evaluated at compile time. This may shift run time errors to compile time. Not to be confused with pure storage (see Pure Storage).
risky-local-variable: If the value is non-nil, the named variable is considered risky as a file-local variable. See File Local Variables.
safe-function: If the value is non-nil, the named function is considered generally safe for evaluation. See Function Safety.
safe-local-eval-function: If the value is non-nil, the named function is safe to call in file-local evaluation forms. See File Local Variables.
safe-local-variable: The value specifies a function for determining safe file-local values for the named variable. See File Local Variables.
side-effect-free: A non-nil value indicates that the named function is free of side effects (see What Is a Function), so the byte compiler may ignore a call whose value is unused. If the property’s value is error-free, the byte compiler may even delete such unused calls. In addition to byte compiler optimizations, this property is also used for determining function safety (see Function Safety).
undo-inhibit-region: If non-nil, the named function prevents the undo operation from being restricted to the active region, if undo is invoked immediately after the function. See Undo.
variable-documentation: If non-nil, this specifies the named variable’s documentation string. This is set automatically by defvar and related functions. See Defining Faces.