# Ball (mathematics)

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In other contexts, such as in Euclidean geometry and informal use, sphere is sometimes used to mean ball. In the field of topology the closed ${\displaystyle n}$-dimensional ball is often denoted as ${\displaystyle B^{n}}$ or ${\displaystyle D^{n}}$ while the open ${\displaystyle n}$-dimensional ball is ${\displaystyle \operatorname {Int} B^{n}}$ or ${\displaystyle \operatorname {Int} D^{n}}$.