A set is the mathematical model for a collection of different things; a set contains elements or members, which can be mathematical objects of any kind: numbers, symbols, points in space, lines, other geometrical shapes, variables, or even other sets. The set with no element is the empty set; a set with a single element is a singleton. A set may have a finite number of elements or be an infinite set. Two sets are equal if they have precisely the same elements.
Bibliography
“Set (Mathematics).” 2022. Wikipedia, December. https://en.wikipedia.org/w/index.php?title=Set_(mathematics)&oldid=1129493353#Subsets.