With a handful of exceptions, each class has a membership predicate word, named class ?. A quotation calling this predicate is stored in the "predicate" word property.

When it comes to predicates, the exceptional classes are:

Class	Predicate	Explanation
f	[ not ]	The conventional name for a word which outputs true when given false is not; f? would be confusing.
object	[ drop t ]	All objects are instances of object
null	[ drop f ]	No object is an instance of null

The set of class predicate words is a class:

predicate

predicate? ( object -- ? )

A predicate word holds a reference to the class it is predicating over in the "predicating" word property.

Implementation of class reloading:

reset-class ( class -- )

forget-class ( class -- )

forget-methods ( class -- )