Ball bearing

For the individual balls used in these bearings, they are sometimes incorrectly referred to as "ball bearings" themselves
Ball bearings are rolling element bearings that use balls to maintain separation between the bearing housing rings.

The purpose of a ball bearing is to reduce rotational friction and to support radial and axial loads. It achieves this by using at least two raceways to accommodate the balls and transfer the load through the balls. In most applications, one housing is fixed while the other is attached to a rotating assembly (e.g., a hub or shaft). When one of the bearing housings rotates, it also causes the balls to rotate. Because the balls are rolling, they have a much lower coefficient of friction than when two flat surfaces slide against each other.

Because of the small contact area between the ball and raceway, ball bearings tend to have a lower load carrying capacity than other types of rolling bearings. However, they can tolerate some misalignment of the inner and outer rings.