pH

Potential of hydrogen (pH) is a scale that measures the acidity or alkalinity of a solution. Values for pH range from 0 (strongly acidic) to 14 (strongly alkaline or basic). The pH of a neutral solution, such as pure water, is 7, whereas the pH of an acidic solution is less than 7 and the pH of a basic solution is greater than 7. The pH scale is logarithmic, meaning that each value is 10 fold the next (for example, a pH of 12 is 10 times more basic than a pH value of 11).

pH is defined by

$pH=-log{\frac {1}{\left[H_{\mathrm {3} }O^{+}\right]}}$