A
set R of ordered pairs of elements of S
such that
(1)
for
all a in S (reflexive property).
(2)
implies 
for all a, b in S
(symmetric
property).
(3)
and 
imply 
for all a, b, c in S (transitive
property).
A
set R of ordered pairs of elements of S
such that
(1)
for
all a in S (reflexive property).
(2)
implies for all a, b in S
(symmetric
property).
(3)
and imply
for all a, b, c in S (transitive
property).