INDICATORS(CLASS X)

pH of a solution is defined as negative logarithm of hyronium ion concentration. pH= -log[ H₃O⁺]
pH is required to judje whether a solution is acidic,basic or neutral
pH=7 , neutral solution , pH>7,basic and pH<7 ,acidic

pH is a measure of the acidity or basicity of a solution.
It is defined as the cologarithm of the activity of dissolved hydrogen ions (H+).
Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations.
The pH scale is not an absolute scale; it is relative to a set of standard solutions whose pH is established by international agreement.
Some references suggest the p stands for “Power”[2], others refer to the German word “Potenz” (meaning power in German)[3], still others refer to “potential”.
Jens Norby published a paper in 2000 arguing that p is a constant and stands for “negative logarithm”[4]; which has also been used in other works[5]. H stands for Hydrogen.

Sørensen suggested the notation "PH" for convenience, standing for "power of hydrogen",[2] using the cologarithm of the concentration of hydrogen ions in solution, p[H][6] Although this definition has been superseded p[H] can be measured if an electrode is calibrated with solution of known hydrogen ion concentration.

Pure water is said to be neutral. The pH for pure water at 25 °C (77 °F) is close to 7.0. Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are said to be basic or alkaline. pH measurements are important in medicine, biology, chemistry, food science, environmental science, oceanography and many other applications.

I thought 'P' Stands for PROTENZ a greek Word meaning Water