A polar molecule is a chemical species in which the distribution of electrons between the covalently bonded atoms is not even. Polarity is a description of how different the electrical poles of a molecule are. If they are highly different, it can be said that the species is a highly polar molecule. Some chemical species, such as chains of carbon molecules, share electrons equally and are said to be nonpolar molecules.

Typically, the designation of whether a molecule is polar or nonpolar comes from the sum of all of its bonds considered together. Each atom has a certain electronegativity. When bonded to another atom, the atom with the higher electronegativity will tend to attract more electrons. If the difference is not great, a nonpolar bond is formed. If the difference is considerable, a polar bond will form and one atom will attract more electrons. In the more extreme cases, the atom with the greater electronegativity will strip the electrons from the first atom and not share them at all. This creates an ionic bond which is simply an attraction between the two species of atom which are positive and negative. Because they do not share electrons, no physical bond connects these species, and they are considered ions in a matrix and not polar molecules.

In chemistry, polarity is a separation of electric charge leading to a molecule or its chemical groups having an electric dipole moment, with a negatively charged end and a positively charged end. Polar molecules must contain polar bonds due to a difference in electronegativity between the bonded atoms.