I. Set notations 
(a) 
Capital letters : A, B, C, S, T 
(b) 
Curly brackets containing a list of elements.
Example : {a, b, c} is the set containing the letters a, b, and c. 
(c) 
Setbuilder notation (see Rolf Pg. 425).
Example : {x  x satisfies property P} where P is any property which makes sense
when applied to x. It may be either easy or difficult to determine whether or not
property P is true for certain values of x. If the determination takes a very
long time, such as a billion years, the set may have uncertain status. 
