A
gyroscope (from
Greek γῦρος
gûros, "circle" and σκοπέω
skopéō, "to look") is a spinning wheel or disc in which the axis of rotation is free to assume any orientation by itself. When rotating, the orientation of this axis is unaffected by tilting or rotation of the mounting, according to the
conservation of angular momentum. Because of this, gyroscopes are useful for measuring or maintaining orientation.