Definition of "rarefaction" [rar•e•fac•tion]

• A decrease in density and pressure in a medium, such as air, caused by the passage of a sound wave. (noun)
• The region in which this occurs. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "But if, for example, the rise in the emulsion to double the rarefaction is a milliard times less than in oxygen, it means that the effective weight of the grain is a milliard times greater than that of the oxygen molecule."
• "He is also studying the process of rarefaction, which is when capillaries and vessels start losing their density."
• "Instead, they used a theoretical approach called rarefaction for gene discovery, a process developed for ecological surveys to determine the abundance of a species in an ecosystem."