Definitions for PH
Random House Webster's College Dictionary
the symbol for the logarithm of the reciprocal of hydrogen ion concentration in gram atoms per liter, used to describe the acidity or alkalinity of a chemical solution on a scale of 0 (more acidic) to 14 (more alkaline).
Origin of pH:
1909; < G P(otenz) potency + H(ydrogen)
pH, pH scale(noun)
(from potential of Hydrogen) the logarithm of the reciprocal of hydrogen-ion concentration in gram atoms per liter; provides a measure on a scale from 0 to 14 of the acidity or alkalinity of a solution (where 7 is neutral and greater than 7 is more basic and less than 7 is more acidic);
The negative of the logarithm to the base 10 of the concentration of hydrogen ions, measured in moles per liter; a measure of acidity or alkalinity of a substance, which takes numerical values from 0 (maximum acidity) through 7 (neutral) to 14 (maximum alkalinity).
Origin: From p, denoting negative logarithm, and H, denoting hydrogen.