Conceptually, method dispatch is implemented by testing the object against the predicate word for every class, in linear order (Class linearization).

Here is an example:

The linear order is the following, from least-specific to most-specific:

Neither class nor generic are subclasses of each other, and their intersection is non-empty. Calling explain with a word on the stack that is both a class and a generic word will print a class word because class is more specific than generic in the class linearization order. (One example of a word which is both a class and a generic word is the class of classes, class, which is also a word to get the class of an object.)

The dispatch-order word can be useful to clarify method dispatch order:

dispatch-order ( generic -- seq )