===== Metric =====
==== Set ====
| @#55CCEE: context     | @#55CCEE: $ X $ ... set |
| @#FFBB00: definiendum | @#FFBB00: $d\in$ it |
| @#55EE55: postulate   | @#55EE55: $d:X\times X \to \mathbb{R}_+$ |
| @#55EE55: postulate   | @#55EE55: $ d(x,y)=0 \implies x=y$ |
| @#55EE55: postulate   | @#55EE55: $ d(x,y)=d(y,x)$ |
| @#55EE55: postulate   | @#55EE55: $ d(x,y)\le d(x,p)+d(p,y)$ |

==== Discussion ====
=== Reference ===
Wikipedia: [[http://en.wikipedia.org/wiki/Metric_%28mathematics%29|Metric]]
==== Parents ====
=== Subset of ===
[[Binary function]]
=== Equivalent to ===
[[Metric space]]
=== Context ===
[[Non-negative real number]]