ABSTRACT
The notion of cardinal numbers and some basic facts about cardinal arithmetic shall be of crucial importance in order to fully understand most of the notions in this monograph. Cardinal numbers are, in some sense, an extension of the natural numbers and cardinal arithmetic is the extension of the basic arithmetic from natural to cardinal numbers. Although our approach here is not intended to be, at all, exhaustive it will surely be sufficient for our purposes. Let us begin by providing the first definition (for any nonempty sets A and B), in which card (A) stands for the cardinality of A.
