Translation of "metric" into Chinese

(mathematics) A measurement of the "distance" between two points in some metric space: it is a real-valued function d ( x , y ) between points x and y satisfying the following properties: (1) "positive definiteness": d(x,y) \ge 0 and d(x,y) = 0 \mbox{ iff } x=y , (2) "symmetry": d(x,y) = d(y,x) , and (3) "triangle inequality": d(x,y) \le d(x,z) + d(z,y) . [..]