Each symbol has a property list on which semi-permanent properties of the symbol can be stored. Each property has a property name or indicator and a value. Property list values are retrieved and set by two functions:
(get < symbol> < propname> )
retrieves the value of the specified property for the specified symbol.
If no such property exists, the value returned is NIL.
(setf (get < symbol> < propname> ) < value> )
sets the value of the specified property for the specified symbol,
displacing any previous value.
Each symbol has a single property list, which appears the same to all parts of a Lisp program and is unaffected by binding.