hydrogen ion concentration(n = noun.attribute) - the number of moles of hydrogen ions per cubic decimeter;
is a kind of concentration
has particulars: ph, ph scale

acid hydrogen, acidic hydrogen, ammonium ion, calcium ion, concentration, concentration camp, heavy hydrogen, hydrogen, hydrogen atom, hydrogen azide, hydrogen bomb, hydrogen bond, hydrogen bromide, hydrogen carbonate, hydrogen chloride, hydrogen cyanide, hydrogen fluoride, hydrogen iodide, hydrogen ion, hydrogen peroxide, hydrogen sulfide, hydroxide ion, hydroxyl ion, ion, ion beam, ion engine, ion exchange, ion pump, molal concentration, molar concentration, potassium hydrogen carbonate, potassium hydrogen tartrate, sodium hydrogen carbonate