Subset

A subset of a set S is a collection of some (perhaps none or all) of the elements of S, at most once each and in no particular order.

To specify a particular subset A of S, one has to decide for each element v of S whether v is in A or v is not in A. Thus we have two choices – v 2 A OR v 62 A – for each element v of S.

Learned in MATH239