This chapter contains some introductory notions concerning the language ofsets, and methods for writing proofs of mathematical statements.

A set is simply a collection of objects, which are called the elements ormembers of the set. There are a number of ways of describing a set. Sometimesthe most convenient way is to make a list of all the objects in the set and putcurly brackets around the list. Thus, for example, {1,3,5} is the set consisting of the objects 1, 3 and 5. {Fred,dog,1.47} is the set consisting of the objects Fred, dog and 1.47. {1,{2}} is the set consisting of two objects, one being the number 1 andthe other being the set {2}.