Electret (formed of elektr- from "electricity" and -et from "magnet") is material that has been permanently electrically charged (polarised). The magnetic equivalent is a permanent magnet.
Polarised material consists of atoms or molecules with electric dipole moment. It can be produced by cooling down material composed of long molecule chains with electric dipole moment so that so-called domains are formed.
Electret materials have recently found commercial and technical interest. For example, they are used in one form of microphone.
See also