The "p" in pH and pOH stands for "negative logarithm of" and is used to make it easier to work with extremely large or small values. pH and pOH are only meaningful when applied to aqueous (water-based) solutions.
pH and pOH denote the negative log of the concentration of hydrogen or hydroxide ions. High pH means that a solution is basic while high pOH means that a solution is acidic. Neutral solutions have pH and pOH of 7. pH pOH acid base concentration.
