Polarity is a measure of the difference in electronegativity between the atoms in a molecule. The greater the difference in electronegativity, the more polar the molecule. Electronegativity is the ability of an atom to attract electrons.

In water, the oxygen atom is more electronegative than the hydrogen atoms. This means that the oxygen atom attracts electrons more strongly than the hydrogen atoms, which creates a polar bond. The oxygen atom has a partial negative charge, and the hydrogen atoms have a partial positive charge. As a result, water has a relatively high polarity.

In methanol, the oxygen atom is also more electronegative than the hydrogen atoms. However, the difference in electronegativity is not as great as it is in water. This means that the polar bond in methanol is not as strong. The oxygen atom has a smaller partial negative charge, and the hydrogen atoms have a smaller partial positive charge. As a result, methanol has a lower polarity than water.