a measure of the acidity or alkalinity of a solution expressed as pH. See pH.
(1) A measure of acidity/alkalinity of a solution. (2) Mathematically is equal to the negative logarithm of the molar concentration of hydrogen ion; measurement of acidity/alkalinity of a solution; pH less than 7 = acidic; above 7 = basic.
The concentration of hydrogen ions in moles per liter of solution; often expressed as pH. (See pH.)