In chemistry, pH is a measure of the acidity or basicity of a liquid solution. It is a scale that ranges from 0 to 14, with 7 being neutral. A pH less than 7 indicates acidity, while a pH greater than 7 indicates basicity or alkalinity. The pH scale is logarithmic, meaning that each number represents a tenfold change in acidity or basicity. The pH of a solution is defined as the negative logarithm of the hydrogen ion concentration, expressed in equivalents per liter. The formula for pH is pH = -log/08%3A_Properties_of_Solutions/8.06%3A_The_pH_Concept). The pH scale is used in many fields, including chemistry, biology, agronomy, medicine, and water treatment. The pH of a solution can be measured using a pH meter, which translates the difference in electromotive force between suitable electrodes placed in the solution into pH readings.