Bond polarity is the uneven distribution of electron density between two bonded atoms that differ in electronegativity. The greater the difference in electronegativity, the more polar the bond. Bond polarity gives rise to partial charges and a bond dipole, which in turn can make the whole molecule polar.

键的极性是电负性不同的两个成键原子之间电子密度的不均匀分布。电负性差异越大,键的极性越强。键的极性产生部分电荷和键偶极,后者又可使整个分子呈极性。