1. : a collection of facts, ideas or entities that is tacitly implied or understood in a given statement, context, or discussion
a proposition concerning “Americans” may be intended to apply only to American aborigines, or to citizens of the U.S., it may include all No. Americans, or be extended to So. Americans as well, the universe of discourse in each case being determined by the sense in which the word is taken
2. : an inclusive class explicitly containing all the entities to be discussed in a given discourse or investigation or theory
the individual variables of an axiom system may be required to range over members of the class of positive integers, which class is the universe of discourse for that system