Definition of quantum
noun (plural quanta /-tə/)
1 Physics a discrete quantity of energy proportional in magnitude to the frequency of the radiation it represents. an analogous discrete amount of any other physical quantity, such as momentum or electric charge. Physiology the unit quantity of acetylcholine released at a neuromuscular junction by a single synaptic vesicle, contributing a discrete small voltage to the measured end-plate potential.
2a required or allowed amount, especially an amount of money legally payable in damages. a share or portion:each man has only a quantum of compassion
