The amplitude of a wave is the maximum displacement of a wave particle from its equilibrium position. In simpler terms, it is the distance from the middle or equilibrium point of a wave to the highest point (crest) or lowest point (trough) of the wave. It represents the amount of energy that is being carried by the wave, with higher amplitude waves carrying more energy than lower amplitude waves. The amplitude of a wave can be measured in various units, such as meters (m), centimeters (cm), or even millimeters (mm), depending on the type of wave being considered.