ABSTRACT
A set is a collection of objects. The objects can be anything: numbers, people, cats, courses, even other sets! The language of sets allows us to talk precisely about events. If S is a set, then the notation x ∈ S indicates that x is an element or member of the set S (and x /∈ S indicates that x is not in S). We can think of the set as a club, with precisely defined criteria for membership. For example:
1. {1, 3, 5, 7, . . . } is the set of all odd numbers; 2. {Worf, Jack, Tobey} is the set of Joe’s cats; 3. [3, 7] is the closed interval consisting of all real numbers between 3 and 7;
4. {HH,HT,TH,TT} is the set of all possible outcomes if a coin is flipped twice (where, for example, HT means the first flip lands Heads and the second lands Tails).
