球冠是指一个球面被平面所截后剩下的曲面。截得的圆面是底，垂直于圆面的直径被截得的部分是高。

也可看作圆弧绕过它的一个端点的圆的直径旋转一周得到的面。

球冠的面积：（R是球半径，h是高）。

与球缺区别：球冠是面，球缺是体，球缺可计算体积而球冠不能。

In geometry, a spherical cap, spherical dome, or spherical segment of one base is a portion of a sphere cut off by a plane. If the plane passes through the center of the sphere, so that the height of the cap is equal to the radius of the sphere, the spherical cap is called a hemisphere.