A characteristic of a gyroscope that causes it to react to an applied force as though the force were applied at a point 90° in the direction of rotation, from the actual point of application.

Precession is the characteristic used in rate gyros. A rate gyro will precess, or lay over in its gimbal, an amount proportional to the rate at which the gimbal is rotated. Rate gyros are the heart of turn and slip indicators and turn coordinators. The rotor of a helicopter acts in much the same way as a gyroscope and is affected by gyroscopic precession.