noun
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A decrease in density and pressure in a medium, such as air, especially when caused by the passage of a wave, such as a sound wave.
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The region in which this occurs.
Other Word Forms
Etymology
Origin of rarefaction
1595–1605; < Medieval Latin rārēfactiōn- (stem of rārēfactiō ), equivalent to Latin rārēfact ( us ) (past participle of rārēfacere; see rarefy) + -iōn- -ion
Explanation
A decrease in the density of something is rarefaction. As you climb a mountain, you experience rarefaction of the air; the air becomes less dense the higher up you go. Most of the time, rarefaction refers to air or other gases becoming less dense. When rarefaction occurs, the particles in a gas become more spread out. You may come across this word in the context of sound waves. A sound wave moving through air is made up of alternating areas of higher and lower density. The areas of lower density are called rarefactions.
Vocabulary lists containing rarefaction
Waves and Wave Properties - Middle School
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Physical Science: Waves, Electricity, and Magnetism
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Waves and Wave Properties - High School
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
In untreated fish, one of the most striking signs of kidney decline was the gradual loss of capillaries, a process known as vascular rarefaction.
From Science Daily ● Jan. 30, 2026
Our analyses were carried out using a modest sequencing depth of 5,000 observations per sample after Deblur and rarefaction.
From Nature ● Oct. 31, 2017
Figure 17.4 As the string moves to the left, it creates another compression and rarefaction as the ones on the right move away from the string.
From Textbooks ● Aug. 12, 2015
This is how noise-canceling headphones work—they produce a sound wave that resembles the wave responsible for the unwanted sound, but with the original phases of rarefaction and compression flipped.
From Scientific American ● Dec. 12, 2013
This is precisely what is meant by rarefaction and condensation.
From A Critical History of Greek Philosophy by W. T. (Walter Terence) Stace
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Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
