The measure of the performance of plate used in an absorption tower or distillation column. The plate is usually perforated to allow vapour or gas to rise up and make contact with liquid. Ideally, a vapour–liquid equilibrium is reached. However, this is not always the case. Due to these contact inefficiencies, more plates are required to achieve a desired separation. The plate efficiency is usually expressed as a percentage of the ideal or theoretical separation. See murphree plate efficiency.