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see harmonic motionharmonic motion,
regular vibration in which the acceleration of the vibrating object is directly proportional to the displacement of the object from its equilibrium position but oppositely directed.
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; wavewave,
in physics, the transfer of energy by the regular vibration, or oscillatory motion, either of some material medium or by the variation in magnitude of the field vectors of an electromagnetic field (see electromagnetic radiation).
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Frequency (wave motion)

The number of times which sound pressure, electrical intensity, or other quantities specifying a wave vary from their equilibrium value through a complete cycle in unit time. The most common unit of frequency is the hertz (Hz), which is equal to 1 cycle per second. In one cycle there is a positive variation from equilibrium, a return to equilibrium, then a negative variation, and return to equilibrium. This relationship is often described in terms of the sine wave, and the frequency referred to is that of an equivalent sine-wave variation in the parameter under discussion. See Frequency measurement, Sine wave, Wave motion

McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.


Symbol: f , ν. The number of oscillations per unit time of a vibrating system. Frequency is measured in hertz. The frequency of a wave is the number of wave crests passing a point per unit time. For light and other electromagnetic radiation, it is related to wavelength λ by ν = c /λ, where c is the speed of light.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



The frequency of an event A is the ratio m/n of the number m of occurrences of A in a given series of trials to the total number n of trials. If the trials are independent and there is a definite probability p of the occurrence of A in an individual trial, then, for arbitrarily small ∊ > 0, at sufficiently large m it is practically certain that the frequency m/n satisfies the inequality


The term “frequency” is used in mathematical statistics to designate the number of elements of a set that have a specified attribute.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


The number of cycles completed by a periodic quantity in a unit time.
The number of times an event or item falls into or is expected to fall into a certain class or category.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


The number of oscillations per second (a) of the current or voltage in an alternating-current electric circuit, or (b) of a sound wave, or (c) of a vibrating solid object; expressed in hertz (abbr. Hz) or in cycles per second (abbr. cps).
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.


frequencyclick for a larger image
i. The number of recurrences of a periodic phenomenon in a unit of time.
ii. The number of cycles completed in one second. One cycle per second is the basic unit of measurement of frequency and is called a hertz.
iii. The number of services operated by an airline per day or per week over a particular route.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved


1. Physics the number of times that a periodic function or vibration repeats itself in a specified time, often 1 second. It is usually measured in hertz.
2. Ecology
a. the number of individuals of a species within a given area
b. the percentage of quadrats that contains individuals of a species
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005


The number of oscillations (vibrations) in one second. Frequency is measured in Hertz (Hz), which is the same as "oscillations per second" or "cycles per second." For example, the alternating current in a wall outlet in the U.S. and Canada is 60Hz. Electromagnetic radiation is measured in kiloHertz (kHz), megahertz (MHz) and gigahertz (GHz). See wavelength, frequency response, audio, carrier and space/time.

The frequency is the number of oscillations per second. The higher the frequency (the closer the ripples would be in this diagram) and the shorter the wavelength.
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References in periodicals archive ?
Le traitement de fond permet de diminuer la frequence de la crise.
EC la menopause, la frequence de l'hypertension chez les femmes rejoint celle des hommes.
Dans une etude prospective, nous avons voulu evaluer l'incidence de la technique Hexvix sur la frequence de detection des tumeurs urotheliales et preciser le profil des tumeurs plus particulierement concernees par le ciblage par Hexvix.
Dans plusieurs etudes, il est aussi observe que la frequence des interventions de gestion educative chez les directions, selon l'evaluation des enseignants, tend a varier, entre autres, en fonction du genre, de l'experience et de la formation (Hallinger, 2008; Hallinger & Murphy, 1985; Kruger, Witziers, & Sleegers, 2007).
Ainsi, la frequence moyenne de l'espece vegetale i dans les feces des males et des femelles (Freq-moy) = nombre d'individus (tous sexes confondus) ayant consomme l'espece vegetale sur le nombre d'individus captures (populations des biotopes ou le vegetal i est inventorie) multiplie par 100.
Les resultats presentes dans cette etude ont ete discutes a l'aide des figures realisees a partir des traitements informatiques qui regroupent toutes les plantes medicinales en fonction de leur frequence d'utilisation (nombre de fois ou une espece vegetale est utilisee par les 400 personnes interrogees).
Layton selon laquelle la structure des arts rupestres differe profondement, entermes de frequence des motifs et de leur distribution entre les sites, en fonction de la religion et de l'organisation sociale des groupes humains est reexaminee dans ce travail collectif, a l'aide d'une documentation renouvelee et augmentee provenant d'Afrique et d'Australie, mais aussi d'une analyse approfondie de l'art parietal paleolithique d'Europe occidentale.
Beginning in June, the Air France Frequence Plus and KLM Flying Dutchman programs will be merged into a single program, called Flying Blue.
In: Telephonie Mobile--Effets Potentiels sur la Sante des Ondes Electromagnetiques de Haute Frequence (Pietteur Marco, ed).
Cityjet, in conjunction with partner Air France, offers Frequence Plus - a loyalty programme where members earn miles based on the distance and class of their trips.