Vibration - An oscillation, or repeating back-and-forth motion, about an equilibrium position.
Wave - A "wiggle in space and time"; a disturbance that repeats regularly in space and time and that is transmitted progressively from one place to the next with no actual transport of matter.
Wave Period - The time in seconds between successive wave crests as they pass a stationary point on the ocean surface, such as a buoy.
Crests - One of the places in a wave where the wave is highest or the disturbance is greatest.
Troughs - One of the places in a wave where the wave is lowest, or the disturbance is greatest, in the opposite direction from a crest.
Amplitude - The distance from the midpoint to the maximum (crest) of a wave or, equivalently, from the midpoint to the minimum (trough).
Wavelength - The distance from the top of the crest of a wave to the top of the following crest, or equivalently, the distance between successive identical parts of the wave.
Frequency - The Number of events (cycles, vibrations, oscillations, or any repeated event) per time; measured in hertz (or events per time). Inverse of period.
Hertz - The SI unit of frequency. One hertz (HZ) is one vibration per second.
Transverse Waves - A wave with vibration at right angles to the direction the wave is traveling.
Longitudinal Waves - A wave in which the vibration is the same direction as that in which the wave is traveling, rather than that at right angles to it.
Doppler Effect - The change in frequency of a wave due to the motion of the source or of the receiver.
Blue Shift - An increase in the measured frequency of light from an approaching source; called the blue shift because the apparent increase is toward the high-frequency, or blue, end of the color spectrum. Also occurs when an observer approaches a source.
Red Shift - A decrease in the measured frequency of light (or other radiation) from a a receding source; called the red shift because the decrease is toward the low-frequency, or red, end of the color spectrum.
Shock Wave - A cone-shaped wave produced by an object moving at supersonic speed through a fluid.
Sonic Boom - The sharp crack heard when the shock wave that sweeps behind a supersonic aircraft reaches the listener.