# Dictionary:Magnetic permeability

The ratio of the magnetic induction ${\textstyle \mathbf {B} }$ to the inducing field strength ${\textstyle \mathbf {H} }$; denoted by the symbol ${\textstyle \mu }$:
${\displaystyle \mu =\mathbf {B} /{\mu }_{o}\mathbf {H} ,}$
where ${\textstyle {\mu }_{o}}$ is the permeability of free space ${\textstyle 4\pi \times 10^{-7}}$ Wb/Am or H/m in SI system, and 1 gauss per oersted in the cgs system with the permeability ${\textstyle \mu }$; dimensionless. The quantity ${\textstyle \mu {\mu }_{o}}$ is sometimes considered the permeability (especially in the cgs system). See Figure M-1.