| Word | Meaning |
| Frequency | The number of vibrations made in one second |
| Hertz (Hz) | The unit in which frequency is counted |
| Kilohertz (kHz) | A unit equal to 1000 hertz |
| Infrasonic sound | Sound of frequency less than 20 Hz |
| Sub sonic | The name given to the wave frequency of infrasonic sound |
| Subsound | Another name for infrasonic sound |
| Audible sound | Sound that a person can hear |
| Ultrasound | Sound of frequency more than 20 kHz |
| Wavelength | The distance between two matching points of a wave |
| Reflection | The turning back of a wave after it strikes a surface |
| Sonar (sound navigation ranging) | The technique of measuring the depth of the sea with sound waves |
| Tumour | An unwanted lump of tissue grown inside the body |