PH Value

The pH value is a measure for the effective H⁺ ion concentration and thus for the strength of the acid or [ basic]] effect of an aqueous solution.

Some mathematics: The pH value corresponds to the negative decadic logarithm of the hydrogen ion concentration, i.e. it is defined as a logarithmic quantity by the decadic logarithm multiplied by -1 (= "ten logarithm") of the oxonium ion concentration (more precisely: the oxonium ion activity).

The term derives from pondus hydrogenii or potentia hydrogenii (lat. pondus, n. = weight; potentia, f. = force; hydrogenium, n. = hydrogen).

https://de.wikipedia.org/wiki/PH-Wert _{(Wikipedia CC-by-sa-3.0)}