In electromagnetism, absolute permittivity is the measure of the resistance that is encountered when forming an electric field in a medium. In other words, permittivity is a measure of how an electric field affects, and is affected by, a dielectric medium. The permittivity of a medium describes how much electric field is 'generated' per unit charge in that medium. More electric flux exists in a medium with a high permittivity because of polarization effects. Permittivity is directly related to electric susceptibility, which is a measure of how easily a dielectric polarizes in response to an electric field. Thus, permittivity relates to a material's ability to transmit an electric field. In SI units, permittivity ε is measured in farads per meter; electric susceptibility χ is dimensionless. They are related to each other through where εr is the relative permittivity of the material, and ε0 = 8.8541878176.. * 10−12 F/m is the vacuum permittivity.