pH
pH (Power of hydrogen) is the number that represents the ratio of H+ (hydrogen) - ions to OH- (oxygen and hydrogen) - ions.

pH stands for numbers 1 to 14. pH below 7 means that the environment is acidic, and above 7 - is alkaline. 7 means that the environment is neutral and the ratio between H + and OH- is equal.
What is the difference between water pH 7, pH 8, and pH 9?
Each subsequent pH-number means that the environment is 10 times more alkaline (more oxygen and hydrogen OH-). If the pH value is greater than 7, then the environment is alkaline (more secured with OH-).
For example pH 8 = 10-times more alkaline than pH 7 and pH 9 = 10-times more alkaline than pH 8.
Conclusion: water with pH 9 is exactly 100-times more alkaline than water with pH 7, and pH 10 is 1000-times more alkaline than pH 7.
The same scheme also applies to the acid environment: pH 4 (more H+ ions) indicates 1000-times more acidic than pH 7, and the environment with pH 3 is 10.000-times more acidic than pH 7.