In chemistry|lang=en terms the difference between polyunsaturated and unsaturated

is that polyunsaturated is (chemistry) of, or relating to long chain organic compounds that have multiple double bonds; polyunsaturated fatty acids are essential to human nutrition while unsaturated is (chemistry) of a compound containing atoms sharing more than one valence bond, especially of an organic compound having one or more double bonds or triple bonds between carbon atoms.

As adjectives the difference between polyunsaturated and unsaturated

is that polyunsaturated is (chemistry) of, or relating to long chain organic compounds that have multiple double bonds; polyunsaturated fatty acids are essential to human nutrition while unsaturated is (chemistry|of a solution) not saturated; capable of dissolving more of a solute at the same temperature.