- A collection of well-defined and distinct objects is called a set.
- Example: the factors of a positive integer is a set
Set_(mathematics) (Wikipedia)
A set of polygons in an Euler diagram
In mathematics, a set is a well-defined collection of distinct objects, considered as an object in its own right. The arrangement of the objects in the set does not matter. For example, the numbers 2, 4, and 6 are distinct objects when considered separately, but when they are considered collectively they form a single set of size three, written as {2, 4, 6}, which could also be written as {2, 6, 4}.
The concept of a set is one of the most fundamental in mathematics. Developed at the end of the 19th century,set theory is now a ubiquitous part of mathematics, and can be used as a foundation from which nearly all of mathematics can be derived.