pOH
Definition
pH's partner scale for hydroxide ions: pOH = -log[OH-]. Low pOH means strongly basic.
Symbol: ·
Technical definition
pOH is the negative base-10 logarithm of hydroxide ion concentration. At 25 C, pH + pOH = 14 (from the water ion product), so either scale fully describes acidity.
Example
A 0.01 M NaOH solution has [OH-] = 0.01 M, so pOH = 2 and pH = 12.
Common confusion
Do not mix up which is which. LOW pOH means HIGH [OH-], which means BASIC: the mirror image of pH's logic.