where ''j'' is the [[imaginary unit]], ''V''(''ω'') is the voltage component at angular frequency ''ω'', ''G''(''ω'') is the ''real'' part of the current, called the ''conductance'', and ''C''(''ω'') determines the ''imaginary'' part of the current and is the ''capacitance''.
:<math> \varepsilon_r(\omega) = \varepsilon '_r(\omega) - j \varepsilon ''_r(\omega) = \frac{1}{j\omega Z(\omega) C_0} = \frac{C_{\text{cmplx}}(\omega)}{C_0} \ , </math> .