What is "electric dipole moment"

n. the dipole moment in an electric dipole

In physics, the electric dipole moment is a measure of the separation of positive and negative electrical charges within a system, that is, a measure of the system's overall polarity. The electric field strength of the dipole is proportional to the magnitude of dipole moment. The SI units for electric dipole moment are Coulomb- meter (C m), however the most commonly used unit is the Debye (D).

Theoretically, an electric dipole is defined by the first-order term of the multipole expansion, and consists of two equal and opposite charges infinitely close together. This is unrealistic, as real dipoles have separated charge. However, because the charge separation is very small compared to everyday lengths, the error introduced by treating real dipoles like they are theoretically perfect is usually negligible.