The measurement used for measuring the strength of an acid is called pH.

Here's why:

* pH stands for "power of hydrogen".

* It measures the concentration of hydrogen ions (H+) in a solution.

* The lower the pH value, the higher the concentration of hydrogen ions, making the solution more acidic.

* A pH of 7 is considered neutral.

* Values below 7 indicate acidity, while values above 7 indicate alkalinity (or basicity).

While pH is the primary measurement for acidity, other related measures are used depending on the context, such as:

* pKa: This measures the tendency of an acid to donate a proton.

* Molarity: This measures the concentration of the acid in a solution.

Let me know if you have any other questions!