Define values for a function f:

These are the downvalues associated with f:

DownValues returns rules corresponding to definitions made for a symbol:

DownValues can be used to set the values directly:

The resulting rules are in the order given:

Now reorder the definitions:

Copy a symbol's definitions to another symbol:

Values can be defined by immediate or delayed assignments:

HoldPattern is used to protect the rules from their own definitions:

Definition and Information display downvalues but do not return them as values:

DownValues returns a value that can be used in a program:

Evaluation of an expression involves applying rules for its head: