frequence

Frequence, typically written as frequency in English and fréquences in French, is the measure of how often a repeating event occurs in a given time. In physics and engineering, the standard meaning is the number of cycles per second, expressed in hertz (Hz). The symbol f is commonly used, and frequency is the reciprocal of the period: f = 1/T. For oscillatory motion, angular frequency ω = 2πf, describing how quickly the phase of a cycle advances.

Frequency can also refer to spatial frequency, measured in cycles per unit distance, used in optics, imaging, and texture analysis. This is an indication of how often a pattern repeats per meter, wavelength, or similar unit.

Common ranges and examples include audio frequencies (roughly 20 Hz to 20 kHz), radio frequencies (kHz to GHz), and optical frequencies (hundreds of THz). In music, pitch corresponds to a particular frequency, with standard tuning placing A4 at 440 Hz. In electronics and communications, frequency determines carrier signals, modulation schemes, and bandwidth.

Measurement and analysis are central to the concept. Frequency counters, oscilloscopes, and spectrum analyzers quantify frequency content. In signal processing, Fourier analysis decomposes a signal into its frequency components, revealing the spectral makeup of a waveform.

Other uses of the term appear in statistics (frequency of events in a data set) and in biology (heart rate or breathing frequency). Frequency can vary over time due to instability, drift, or Doppler effects, and is thus often described as variable or time-dependent.