The distance an Electromagnetic Wave travels in the time it takes to oscillate through a complete cycle. (2) Wavelength (symbol ?) = 1/frequency. In general, the mean distance between maximums (or minimums) of a roughly periodic pattern. Specifically, the shortest distance between particles moving in the SAME phase of oscillation in a wave disturbance. (3) The length of one complete wave of an alternating or vibrating phenomenon, generally measured from crest to crest or from trough to trough of successive waves.