Vibration: an oscillation, or repeating back-and-fourth motion, about an equilibrium position.
Wave: 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 it takes for two successive wave crests to pass a given point.
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 (troughs).
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, oscillation, 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 in the same direction as that in which the wave is traveling, rather than 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. Name was because the apparent increase is towards 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 from a receding source. Name was 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.