A metric space is a set with a global distance function
(the metric
) that, for every two points
in
, gives the distance between them
as a nonnegative real
number
.
A metric space must also satisfy the following conditions for
all
(Rudin 1976, p. 30; Munkres 2000, p. 119):
1. iff
,
2. ,
3. The triangle inequality .