Mass-to-charge ratio

The mass-to-charge ratio is a physical quantity (it is an amount that can be measured). The SI unit is kg/C, which is kilograms divided by the coulomb. Sometimes the charge-to-mass ratio is used instead.
In a vacuum, all particles with the same mass-to-charge ratio move in the same path, when in the same strength of electric and magnetic fields.
It is important for things like mass spectrometry.