Vibration - an oscillation of the parts of a fluid or an elastic solid whose equilibrium has been disturbed, or of an electromagnetic wave.
Wave - a periodic disturbance of the particles of a substance that may be propagated without net movement of the particles, such as in the passage of undulating motion, heat, or sound.
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 - The point on a wave with the maximum value or upward displacement within a cycle.
Troughs - The minimum point in a wave or an alternating signal.
Amplitude - The maximum extent of a vibration or oscillation, measured from the position of equilibrium.
Wavelength - The distance between successive crests of a wave, especially points in a sound wave or electromagnetic wave.
Frequency - The number of times that a periodic function or vibration repeats itself in a specified time, often 1 second (usually measured in hertz).
Hertz - The SI unit of frequency, equal to one cycle per second.
Transverse waves - Waves that vibrate at right angles to the direction of their propagation.
Longitudinal waves - Waves vibrating in the direction of propagation.
Doppler Effect - An increase (or decrease) in the frequency of sound, light, or other waves as the source and observer move toward (or away from) each other. The effect causes the sudden change in pitch noticeable in a passing siren, as well as the redshift seen by astronomers.
Blue shift - A shift toward shorter wavelengths of the spectral lines of a celestial object, caused by the motion of the object toward the observer.
Red shift - A shift toward longer wavelengths of the spectral lines emitted by a celestial object that is caused by the object moving away from the earth.
Shock wave - A region of abrupt change of pressure and density moving as a wave front at or above the velocity of sound.
Sonic boom - A loud explosive noise caused by the shock wave from an aircraft traveling faster than the speed of sound.