pH 
/ˈpi:ˈeɪtʃ/ noun
/ˈpi:ˈeɪtʃ/ noun [singular] technical : a number between 0 and 14 that indicates if a chemical is an acid or a base ◊A chemical with a pH lower than 7 is an acid, and a chemical with a pH higher than 7 is a base.
▪ You should test the pH of the soil in your garden.
▪ You should test the pH of the soil in your garden.
