Dynamic Magnifier: This is function of frequency ratio.

Forced Vibration: While the system is continuously excited by an external force or internally produced force, the vibrations are known as forced vibration.

Whirling of Shaft: While a shaft carrying inertia rotates, the whole shaft system rotates around an axis passing through bearing centres. This rotation is known as whirling of shaft.

Synchronous Whirl: While angular speed of rotation of the shaft is equivalent to the whirling speed and in the similar senses it is case of synchronous whirl.

Non-synchronous Whirl: While angular speed of the shaft is not equivalent to the whirling speed, it is known as non-synchronous whirl.