## metricAny function d( x, y) that describes the distance between two
points. Distance is formally defined as a single number with the following
properties: (1) d(x, y) = 0 if and only if x = y;
(2) d(x, y) = d(y, x); (3) d(x, y)
+ d(y, z) > or = d(x, z) (the triangle inequality).
The concept of a metric is important in differential
geometry. Metric space is a set that has a metric;
in other words, a kind of space in which the concept of distance has meaning.
Compare with topological space. ## Related categories• GEOMETRY• GRAVITATIONAL PHYSICS • SPACE AND TIME | |||||

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