pH measures the acidity or basicity of an aqueous solution. It is mathematically defined as:
$$\text{pH} = -\log_{10}[H^+]$$
For bases, we calculate $pOH$ where $\text{pH} + \text{pOH} = 14$.
Can pH be higher than 14?
Yes, extremely concentrated bases can result in a pH above 14.
Is temperature important?
Yes, $K_w$ changes with temperature, which shifts the neutral point away from exactly 7.0.