In a medium of dielectric constant K, the electric field is E. If $ε_0$ is permittivity of the free space, the electric displacement vector is

$Kε_0E$

The electric displacement field is a vector valued D that accounts for the effects of bound charges within materials. In general D is given by

$D = ε_0 E + P$

When E is electric field, $ε_0$ the vacuum permittivity and P the polarization density of the material.

In most ordinary terms

$D = ε_0E$

When dielectric is present $ε = K ε_0$

$∴ D = Kε_0 E$