Question

what is universal set ?

Answer 1

A universal set is the collection of all objects in a particular context or theory. All other setsin that framework constitute subsets of the universal set, which is denoted as an uppercase italic letter U. The objects themselves are known as elements or members of U

Answer 2

In mathematics, and particularly in set theory and the foundations of mathematics, auniverse is a class that contains (as elements) all the entities one wishes to consider in a given situation