noun, plural fre·quen·cies.
- Also fre·quence. the state or fact of being frequent; frequent occurrence: We are alarmed by the frequency of fires in the neighborhood.
- rate of occurrence: The doctor has increased the frequency of his visits.
- the number of periods or regularly occurring events of any given kind in unit of time, usually in one second.
- the number of cycles or completed alternations per unit time of a wave or oscillation. Symbol: F; Abbreviation: freq.
- Mathematics. the number of times a value recurs in a unit change of the independent variable of a given function.
- Statistics. the number of items occurring in a given category.
noun plural -cies
- the state of being frequent; frequent occurrence
- the number of times that an event occurs within a given period; rate of recurrence
- 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 hertzSymbol: ν, f
- the number of individuals in a class (absolute frequency)
- the ratio of this number to the total number of individuals under survey (relative frequency)
- the number of individuals of a species within a given area
- the percentage of quadrats that contains individuals of a species
1640s, “fact of occurring often,” from Latin frequentia “a crowding, crowd,” from frequentem (see ).
Earlier it had been used in a now-obsolete sense of “state of being crowded” (mid-16c.); sense in physics, “rate of recurrence,” especially of a vibration, is from 1831. In radio electronics, frequency modulation (1922, abbreviated F.M.) as a system of broadcasting is distinguished from amplitude modulation (or A.M.).
- Physics The rate at which a repeating event occurs, such as the full cycle of a wave. Frequencies are usually measured in hertz. Compare amplitude. See also period.
- Mathematics The ratio of the number of occurrences of some event to the number of opportunities for its occurrence.
In, the number of crests of a that move past a given point in a given unit of time. The most common unit of frequency is the ( ), corresponding to one crest per second. The frequency of a wave can be calculated by dividing the speed of the wave by the . Thus, in the , the wavelengths decrease as the frequencies increase, and vice versa.