Meaning & use
rarefaction
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Meanings
noununcountable
a decrease in the density or pressure of a substance, especially air, as in a sound wave
Grammar: Uncountable in physics; can be countable when referring to a specific instance ('a rarefaction').
Patterns
- rarefaction of air
- rarefaction and compression
- a region of rarefaction
In a sound wave, rarefaction is the part where air particles spread apart.
The diagram shows compression and rarefaction alternating along the wave.
Rarefaction of the gas occurs when the piston moves outward quickly.
noununcountabletechnical
the process of making something less dense or less concentrated
Grammar: Used in general scientific writing; often followed by 'of'.
Patterns
- rarefaction of something
- the rarefaction of gases
The rarefaction of the upper atmosphere means there is less oxygen to breathe.
Scientists studied the rarefaction of the metal under extreme heat.
Word forms
| plural | rarefactions |
|---|
Common combinations
- compression and rarefaction
- Sound travels through air as a series of compression and rarefaction waves.
- rarefaction of the air
- At high altitudes, the rarefaction of the air makes breathing difficult.
- a region of rarefaction
- The microphone detects changes in pressure in a region of rarefaction.
- rarefaction wave
- A rarefaction wave moves through the material after the explosion.
Synonyms and how they differ
- decompression
- Decompression is a more general term for reducing pressure; rarefaction is used specifically in physics for density changes in waves or gases.
- thinning
- Thinning is an everyday word for making something less dense, while rarefaction is the technical term used in science.
Opposites
Word family
- rarefy verb
- to make or become less dense
- rarefied adjective
- less dense than usual; also used figuratively for exclusive or lofty
Commonly confused: rarefaction or rarefaction vs refraction? rarefaction or rarefaction vs compression?
rarefaction vs rarefaction vs refraction
Refraction is the bending of light or sound when it passes between materials; rarefaction is about density changes within a wave.
rarefaction vs rarefaction vs compression
Compression is an increase in density; rarefaction is the opposite—a decrease.
Practice
In a sound wave traveling through air, what does rarefaction refer to?
Choose one answer.
Rarefaction is the part of the wave where air particles are less dense (spread apart). The packed-together region is compression, and bending is refraction.
Make it your own
Write a sentence using “rarefaction”, then check it and compare it with the examples above.