Etymology
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frequency (n.)
1550s, "state of being crowded" (now obsolete); 1640s, "fact of occurring often;" from Latin frequentia "an assembling in great numbers, a crowding; crowd, multitude, throng," from frequentem (see frequent). 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.).
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absolute (adj.)
Origin and meaning of absolute

late 14c., "unrestricted, free from limitation; complete, perfect, free from imperfection;" also "not relative to something else" (mid-15c.), from Latin absolutus, past participle of absolvere "to set free, acquit; complete, bring to an end; make separate," from ab "off, away from" (see ab-) + solvere "to loosen, untie, release, detach," from PIE *se-lu-, from reflexive pronoun *s(w)e- (see idiom) + root *leu- "to loosen, divide, cut apart."

Sense evolution probably was from "detached, disengaged" to "perfect, pure." Meaning "despotic" (1610s) is from notion of "absolute in position;" absolute monarchy is recorded from 1735 (absolute king is recorded from 1610s). Grammatical sense is from late 14c.

Absolute magnitude (1902) is the brightness a star would have at a distance of 10 parsecs (or 32.6 light years); scientific absolute value is from 1907. As a noun in metaphysics, the absolute "that which is unconditional or free from restriction; the non-relative" is from 1809.

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absolute zero (n.)
"lowest possible temperature which the nature of heat admits" (determined to be –273 centigrade, –458 Fahrenheit), the idea dates back to 1702 and its general value was guessed to within a few degrees soon thereafter, but not precisely discovered until Lord Kelvin's work in 1848. It was known by many names, such as infinite cold, absolute cold, natural zero of temperature; the term absolute zero was among them by 1806.
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VHF 
1932, initialism (acronym) of very high frequency.
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ultrasonic (adj.)
"having frequency beyond the audible range," 1923, from ultra- "beyond" + sonic. For sense, see supersonic.
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UHF 
1937, abbreviation of ultra-high frequency (1932) in reference to radio frequencies in the range of 300 to 3,000 megahertz.
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autarchy (n.)
1660s, "absolute sovereignty," from Latinized form of Greek autarkhia, from autarkhein "to be an absolute ruler," from autos "self" (see auto-) + arkhein "to rule" (see archon).
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F.M. 

1922, abbreviation of frequency modulation as a method of encoding information in radio waves by varying the frequency of the wave. As a method of broadcasting radio programs, it began in the late 1930s and was notable for superior noise reduction and the capability of broadcasting in stereo. As the chosen medium for broadcasting stereo rock music it became popular in the 1970s.

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racial (adj.)

"relating, pertaining to, or characteristic of an ethnic race or race generally," 1862, from race (n.2) + -ial. "A word of considerable frequency in the 20th century" [OED]. Related: Racially.

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Hertz 
unit of frequency equal to one cycle per second, 1928, named in reference to German physicist Heinrich Hertz (1857-1894). Related: Hertzian.
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