A gyroscope (from Ancient Greek γῦρος gŷros , "round" and σκοπέω
skopéō , "to look") is a device used for measuring or maintaining
orientation and angular velocity. It is a spinning wheel or disc in which the
axis of rotation (spin axis) 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.
Gyroscopes based on other operating principles also exist, such as the
microchip-packaged MEMS gyroscopes found in electronic devices (sometimes
called gyrometers ), solid-state ring lasers, fibre optic gyroscopes, and
the extremely sensitive quantum gyroscope.