x1 (the acidity/hydrogen activity of a solution) measures x2 in pH according to scale (si'o) x3 using logarithmic base x4 (default: ten)
x1 should not be an object/solution itself (that would be sumti-raising), but rather its acidity/basicness/hydrogen activity; in theory, something other than hydrogen activity could be measured (in which case, it would no longer truly be pH but, for some substance X, actually pX). x3 should specify a reference acidity and its associated pH value (for example: pure water has a pH of exactly 7), the meaning of changing the pH by 1, and in which direction basicness (xor acidity) increases (traditionally: toward positive infinity is representative of relativelt increasingly basicness); x2 can be any real number (not just restricted to the interval from 0 to fourteen), so long as it is pure (dimensionless).