An ordered pair is a pair of mathematical objects for which the order of those objects is significant.
For objects and
, the ordered pair with
as the first element and
as the second is denoted:
.
Since the order is important, =
if and only if
and
. This also means that the ordered pair
is only equal to its reverse,
, when
.
This enforced order is one way in which ordered pairs are different from sets, whose order does not matter. ie., .