Main Entry: pH

Pronunciation: \ˈpē-ˈāch\

Function: noun

Etymology: German, from Potenz power + H (symbol for hydrogen)

Date: 1909

: a measure of acidity and alkalinity of a solution that is a number on a scale on which a value of 7 represents neutrality and lower numbers indicate increasing acidity and higher numbers increasing alkalinity and on which each unit of change represents a tenfold change in acidity or alkalinity and that is the negative logarithm of the effective hydrogen-ion concentration or hydrogen-ion activity in gram equivalents per liter of the solution; also : the condition represented by a pH number