What is the SI unit of relative permittivity ($\epsilon_r$) of a dielectric medium?

Relative permittivity (also called the dielectric constant, $\epsilon_r$ or $k$) is defined as the ratio of the absolute permittivity of a dielectric material ($\epsilon$) to the permittivity of free space (vacuum, $\epsilon_0$):

Because it is the ratio of two physical quantities sharing identical units (Farads per meter, $\text{F/m}$), the units cancel out completely. Therefore, relative permittivity is a purely dimensionless and unitless scalar quantity.

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