Hardness:- It shows the amount of multivalent ions mostly comprised of Calcium and Magnesium dissolve in water.

Definition:- Property of water by which it does not produce lather when reacting with soap.

Hard water contains a high amount of Calcium, Magnesium (Chloride, sulfate, carbonate, and bicarbonate) or any other metal iron. Whereas Soft water contains very less or Nill amount of this salt.