Science, Tech, Math › Science Frequency Definition in Science Share Flipboard Email Print Andrey Prokhorov / Getty Images Science Chemistry Chemical Laws Basics Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated May 03, 2019 In the most general sense, frequency is defined as the number of times an event occurs per unit of time. In physics and chemistry, the term frequency is most often applied to waves, including light, sound, and radio. Frequency is the number of times a point on a wave passes a fixed reference point in one second. The period or duration of time of a cycle of a wave is the reciprocal (1 divided by) of frequency. The SI unit for frequency is the Hertz (Hz), which is equivalent to the older unit cycles per second (cps). Frequency is also known as cycles per second or temporal frequency. The usual symbols for frequency are the Latin letter f or the Greek letter ν (nu). Examples of Frequency Although the standard definition of frequency is based on events per second, other units of time may be used, such as minutes or hours. For example, a human heart may beat at a frequency of 68 beats per minute.A 78 record on a turntable turns at the rate of 78 revolutions per minute or 78 rpm.