铁电性是某些材料存在自发极化，并在外加电场的作用下可以被反转的特性。

多数材料的极化是与外加电场成线性正比的，非线性效应是不显著的。这种极化叫做介电极化。有些称作顺电体的材料，其线性之极化效应更加显著。于是与极化曲线斜率相对应的介电常数为一个外加电场之函数。除了非线性效应外，铁电材料中还存在自发极化。铁电材料的不同之处在于它的自发极化可以在外加电场作用下被反转，产生一个电滞曲线。

一般来说，材料的铁电性只存在于某一相应温度以下，称为居里温度。在这个温度以上，材料变为顺电体。

Ferroelectricity is a property of certain materials that have a spontaneous electric polarization that can be reversed by the application of an external electric field. The term is used in analogy to ferromagnetism, in which a material exhibits a permanent magnetic moment. Ferromagnetism was already known when ferroelectricity was discovered in 1920 in Rochelle salt by Valasek. Thus, the prefix ferro, meaning iron, was used to describe the property despite the fact that most ferroelectric materials do not contain iron.