Noun

(frequencies)

(uncountable) The rate of occurrence of anything; the relationship between incidence and time period.

* With growing confidence, the Viking’s raids increased in frequency .

* The frequency of bus service has been improved from 15 to 12 minutes.

(uncountable) The property of occurring often rather than infrequently.

* The FAQ addresses questions that come up with some frequency .

* The frequency of the visits was what annoyed him.

(countable) The quotient of the number of times $n$ a periodic phenomenon occurs over the time $t$ in which it occurs: $f\; =\; n\; /\; t$.

* The frequency of the musical note A above middle C is 440 oscillations per second.

* ''The frequency of a wave is its velocity $v$ divided by its wavelength $\backslash lambda$: $f\; =\; v\; /\; \backslash lambda$.

* Broadcasting live at a frequency of 98.3 megahertz, we’re your rock alternative!

* The frequency for electric power in the Americas is generally 60 Hz rather than 50.

(statistics) number of times an event occurred in an experiment (absolute frequency)

Noun

(en-noun)

Specter, apparition.

A range; a continuous, infinite, one-dimensional set, possibly bounded by extremes.

* {{quote-news, year=2012, date=November 7, author=Matt Bai, title=Winning a Second Term, Obama Will Confront Familiar Headwinds, work=New York Times citation

, passage=As Mr. Obama prepared to take the oath, his approval rating touched a remarkable 70 percent in some polling — a reflection of good will across the political spectrum .}}

Specifically, a range of colours representing light (electromagnetic radiation) of contiguous frequencies; hence electromagnetic spectrum, visible spectrum, ultraviolet spectrum, etc.

* 2010 October 30, Jim Giles, Jammed!'', in '' ,

Current 3G technologies can send roughly 1 bit of data - a one or a zero - per second over each 1 Hz of spectrum that the operator owns.

(chemistry) The pattern of absorption or emission of radiation produced by a substance when subjected to energy (radiation, heat, electricity, etc.).

(mathematics, linear algebra) The set of eigenvalues of a matrix.

(mathematics, functional analysis) Of a bounded linear operator A'', the set of scalar values ? such that the operator ''A—?I'', where ''I denotes the identity operator, does not have a bounded inverse; intended as a generalisation of the linear algebra sense.