noun

set theorya collection of distinct objects."the set of natural numbers contains 1, 2, 3, and so on."
A set in mathematics is a collection of distinct objects. These objects can be anything: numbers, functions, other sets, and so on. The objects within a set are called elements or members of the set.
For example, is a finite set of numbers with three elements.
The concept of sets is fundamental in mathematics and forms the basis of a branch called set theory, which is used as a foundational system for nearly all of mathematics.
A set of numbers is a collection of numbers grouped together based on specific properties. Common sets of numbers include the natural numbers, integers, rational numbers, real numbers, and complex numbers.