9.2.4 define command

The define command defines an identifier as a number. This is useful to give a symbolic name to a constant used in more than one character or fontdimen definition, for ease of change. It has the form:

define id expr

The identifier id is defined to be the expression expr. Any previous definition of id is replaced. The id can be used prior to the define command; Charspace doesn't try to resolve any definitions in the CMI files until after all files have been read.