Definition:Ball


 * Definition:Open Ball
 * Definition:Closed Ball
 * Definition:Unit Ball
 * Definition:Open Unit Ball
 * Definition:Closed Unit Ball

Also known as
Some sources use the term disk (or disc in British English), but prefers to reserve this term for a disk in the complex plane, as there is an intuitive $2$-dimensional nuance to the word disk.

Also see

 * Definition:Disk
 * Definition:Sphere
 * Definition:Circle