| Term | Definition |
| mechanical wave | a wave that travels only through matter |
| electromagnetic wave | a wave that can travel through empty space or through matter |
| transverse wave | a wave in which the disturbance is perpendicular to the direction the wave travels |
| longitudinal wave | a wave that makes the particles of a medium move back and forth parallel to the direction the wave travels |
| frequency | the number of wavelengths that pass a point each second |
| amplitude | the maximum distance a wave varies from its rest position |
| refraction | the change in direction of a wave as it changes speed, moving from one medium into another |
| radio wave | a low-frequency, low- energy electromagnetic wave that has a wavelength longer than 30 cm |
| infrared wave | an electromagnetic wave with a wavelength shorter than a microwave but longer than light |
| ultraviolet | an electromagnetic wave with a slightly shorter wavelength and a higher frequency than light |
| transparent | a material that allows almost all of the light striking it to pass through, and through which objects can be seen clearly |
| translucent | a material that allows most of the light that strikes it to pass through, but through objects appear blurry |
| opaque | a material through which light does not pass |
| intensity | the amount of energy that passes through a square meter of space in one second |
| compression | region of a longitudinal wave where the particles are closest together |
| rarefraction | region of the longitudinal wave where the particles are farthest apart |
| pitch | the perception of how high or low a sound seems |
| decibel | the unit used to measure sound intensity, or loudness, |
