What does a molecular dipole moment measure?

In the context of chemical bonding, a molecular dipole moment measures the polarity of a molecule, specifically reflecting the magnitude and distribution of its electrical charge.12

For a heteronuclear bond, the dipole moment ($\mu$) is defined as the product of the magnitude of the partial charges on the bonded atoms and the distance of their separation (the bond length). Because electrons are not shared equally between atoms of different electronegativities, the more electronegative atom acquires a partial negative charge, while the other acquires a partial positive charge, creating an electric dipole.12

For a polyatomic molecule, the overall molecular dipole moment is determined by both the polarity of its individual bonds and the molecule's geometric shape. If the bond dipoles are arranged such that they do not cancel each other out—as seen in the angular structure of a water molecule—the molecule possesses a nonzero dipole moment and is considered polar. Conversely, in a linear molecule like carbon dioxide, the bond dipoles may point in opposite directions and cancel, resulting in a nonpolar molecule.12