3 Slots

An instance has zero or more named slots; the name of a slot is a symbol. The slots of an instance are determined by its class.

Each slot can hold one value. When a slot does not have a value, the slot is said to be uninitialized. The default initial value for a slot is defined by the initial-value and initializer slot properties.

A slot is said to be accessible in an instance of a class if the slot is defined by the class of the instance or is inherited from a superclass of that class. At most one slot of a given name can be accessible in an instance. Slots are accessed by means of slot-access methods (usually generated by make-class).