Frequency

[Luis Fok]

The condition of returning frequently; occurrence often
repeated; common occurence; as, the frequency of crimes; the frequency
of miracles.

[Greta]

Frequency measures the number of times something occurs in a specific amount of time. For example, if someone visits the grocery store twice a week, her shopping frequency is 2 visits per week. While frequency can be used to measure the rate of any action, in technical applications it is typically used to measure wave rates or processing speed. These frequencies often occur multiple times per second and therefore are measured in hertz (Hz) or related units of measurement, such as megahertz or gigahertz.
Frequency can be used to measure the rate of waves, such as sound waves, radio waves, and light waves. Audible sound waves have a frequency of roughly 20 Hz to 20,000 Hz (20 kilohertz). Therefore, the sounds you hear have waves that occur anywhere from 20 to 20,000 times per second. Lower frequencies produce low-pitched sounds and are called bass frequencies. Higher frequencies produce high-pitched sounds and are called treble frequencies.
Sound waves are compression waves, which actually move small amounts of air particles. Other waves, such as radio waves and light waves do not require air particles to travel. These waves are part of the electromagnetic spectrum and generally have much higher frequencies than sound waves. For example, most radio waves are measured in megahertz (1,000,000 hertz) or gigahertz (1,000,000,000 hertz). Visible light has a frequency of about 400 terahertz to 780 terahertz.
In the computer world, frequency is often used to measure processing speed. For example, clock speed, measures how many cycles a processor can complete in one second. If a computer has a 3.2GHz processor, it can can complete 3,200,000,000 cycles per second. FLOPS, which is used to measure floating point performance, is also a frequency-based calculation (operations per second). Finally, computing speed may also be defined in MIPS, which measures instructions per second.

[Sonia]

Teh internet serious [dewd] of supreme [1337ness], who is like teh [rox0rz] omfg!

[Kit]

Measured in hertz (cycles per second), rate of repetition of changes / waves.
The term frequency is also used for range (band) on the radio frequency spectrum, such as 800 MHz, 900 MHz or 1900 MHz.

[Hina Muqadas]

The rate at which something occurs or is repeated over a particular period of time or in a given sample.