ABSTRACT
A binary relation B on the set X is formally defined as a subset of X x X - write B Ç I x I , and (x ,y ) G B if the ordered pair (ar,y) is in the relation B . Another, quicker way to write (a;,y) G B is x i?y , which can be read as “ x Bees y” or ux stands in the relation B to y .” If (x ,y) ^ B , I’ll write “not x B y ” or xJ9y.
