A plot of a variable related to a relevant concentration (activity) as the ordinate vs. some measure of the amount of titrant, usually titration volume (titre) as the abscissa. If the variable is linearly related to concentrations, such as the electrical conductance or the photometric absorbance, the term linear titration curve is used. When a logarithmic expression of the concentration or activity is used, such as the pH, pM, or the electrical potential in mV, the curve is referred to as a logarithmic titration curve.