Measure of unit increase or decrease that is actually a tenfold increase or decrease in the quantity measured. For example, a pH reading of 5 pH indicates 10 times the acidity of 4 pH, and 100 times the acidity of 3 pH; 1/10th the acidity of 6 pH, and 1/100th the acidity of 7 pH. (Refer to pH scale.)
Black’s Law Online Dictionary
