/ ˌpiː ˈeɪtʃ; NAmE / noun
[ sing. ] ( chemistry ) a measurement of the level of acid or alkali in a solution or substance. In the pH range of 0 to 14 a reading of below 7 shows an acid and of above 7 shows an alkali :
a pH of 7.5
to test the pH level of the soil
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WORD ORIGIN
early 20th cent.: from p representing German Potenz power + H , the symbol for hydrogen.