A wave is a disturbance traveling through a medium, a function varying both in time and position. Mechanical waves propagate by virtue of the elastic and inertial properties of their medium. Light is a form of wave which propagates by virtue of the electric and magnetic properties of space. Keep in mind that as a wave passes, it is energy that is moving. After the wave has passed, displacements in the medium return to zero.
In one form or another, the topic of Waves comes up on nearly every MCAT. There are usually going to be a few uncomplicated waves problems. The test-writers will make sure you know how to move between wavelength, wave speed, and frequency, for example. Usually these simple questions are nested within a discussion of a more advanced scenario from wave optics or modern physics, for example. Occassionaly, one might run into a waves passage that represents a more advanced take on a familiar topic, such as two dimensional standing waves on a drumhead or a complex seismic wave. With waves as with most topics,the MCAT likes to give you unfamiliar, difficult-seeming phenomena and then ask questions which are pretty easy if you know the fundamentals.
Conceptual Vocabulary Self-Test
Basic Terms Crossword Puzzle
Basic Puzzle Solution
Conceptual Vocabulary for Waves