Sphere ($S^2$, 2-sphere)

The term "Sphere" can refer to different concepts depending on the context. Here are some common interpretations: 1. **Geometric Shape**: A sphere is a three-dimensional geometric object that is perfectly round, where all points on its surface are equidistant from its center. It is defined in mathematics and is commonly represented in equations such as \(x^2 + y^2 + z^2 = r^2\), where \(r\) is the radius of the sphere.