Dieletric

[1] In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised via an electric field. if a dielectric material is placed in an electric field, electric charges won't flow through the material as they do in an electrical conductor, as they have no loosely bound, or free, electrons that may drift through the material, but instead they shift, only slightly, from their average equilibrium positions, causing dielectric polarisation.

Due to dielectric polarisation, positive charges are displaced in the field's direction and negative charges shift in the opposite direction to the field, creaing an internal electric field reducing the overall field in the dielectric itself. If a dielectric is made of weakly bonded molecules, those molecules become polarised and reorient so that their symmetry axes align to the field.