# diameter

Let $A$ a subset of a pseudometric space $(X,d)$. The diameter of $A$ is defined to be

 $\sup\{d(x,y):x\in A,y\in A\}$

whenever the supremum exists. If the supremum doesn’t exist, diameter of $A$ is defined to be infinite.

Having finite diameter is not a topological invariant.

Title diameter Diameter 2013-03-22 12:20:36 2013-03-22 12:20:36 drini (3) drini (3) 4 drini (3) Definition msc 54-00 Pi