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pH is a measure of the acidity or basicity (alkalinity) of a solution. It is defined as the negative logarithm (base 10) of the concentration of hydrogen ions (H+) in a solution. The pH scale ranges from 0 to 14, where a pH of 7 is considered neutral, values less than 7 are acidic, and values greater than 7 are basic or alkaline. Pure water has a pH of 7, which is considered neutral. The pH of a solution can have important implications for many chemical and microbiological degradation processes.