A polar molecule is a type of molecule that has a net dipole moment, which means that the molecule has a positive and negative end due to the distribution of its electrons. Synonyms for the term include dipolar molecule, polarized molecule, or simply polar compound. Additionally, polar molecules are often contrasted with nonpolar molecules, which are characterized by a more even distribution of electrons across the molecule. Examples of polar molecules include water (H2O) and ammonia (NH3), while examples of nonpolar molecules include methane (CH4) and carbon dioxide (CO2). Understanding the nature of polar and nonpolar molecules is important in fields such as chemistry and biology.