solutions. While the origin of the symbol 'pH' can be traced back to its original inventor, and the 'H' refers clearly to hydrogen, the exact original meaning of the letter 'p' in pH is still disputed; it has since acquired a more general technical meaning that is used in numerous other contexts.

The pH scale is logarithmic and inversely indicates the activity of hydrogen cations in the solution
: where [H⁺] is the equilibrium