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

In chloroform, the difference in electronegativity between carbon and chlorine is 0.5. In diethyl ether, the difference in electronegativity between oxygen and carbon is 1.0. Therefore, diethyl ether is more polar than chloroform.

The polarity of a molecule can also be affected by the shape of the molecule. In general, molecules with a symmetrical shape are less polar than molecules with an asymmetrical shape. Chloroform has a symmetrical shape, while diethyl ether has an asymmetrical shape. Therefore, diethyl ether is more polar than chloroform.