The pH value is a measure of the acidity or alkalinity of a solution. It indicates how many hydrogen ions (H⁺) are present in the solution. The pH value ranges from 0 to 14, with a value of 7 considered neutral. Values below 7 indicate acidic solutions, while values above 7 indicate alkaline solutions. A low pH value means a high concentration of hydrogen ions and thus a strong acid, while a high pH value indicates a low concentration of hydrogen ions and thus a strong base. The pH value is important in chemistry, biology, environmental science, and medicine, as many chemical reactions and biological processes depend on the pH value.