▾ Set of symbols
▾ Alphabet
▾ Deduction system
▾ Theory
▾ Zermelo-Fraenkel set theory
▾ Set
▾ Binary cartesian set product
▾ Binary relation
▾ Map
▾ Operation
▾ N-operation
▾ Binary operation
▾ Basic binary operation
▾ Unsigned basic binary operation
▾ Semimetric
▾ Metric
▾ Metric space
Empty metric space
Formulation 0
An D548: Ordered pair $M = (X, d)$ is an empty metric space if and only if
(1) $X = \emptyset$ (D13: Empty set)
(2) $d$ is an D219: Empty map