Set

A group of numbers, variables, geometric figures, or just about anything. Sets are written using set braces {}. For example, {1,2,3} is the set containing the elements 1, 2, and 3.

Note: Order does not matter in a set. The sets {a,b,c} and {c,a,b} are the same set. Repetition does not matter either, so {a,b} and {a,a,b,b,b} are the same set.