vis·​cos·​i·​ty | \ vi-ˈskä-sə-tē \
plural viscosities

Definition of viscosity

1 : the quality or state of being viscous : a sticky or glutinous consistency
2a technical : the property of resistance to flow in any material with fluid properties … water has a small but measurable viscosity, or "stickiness," which results from the weak mutual attraction of water molecules.— Hans Christian von Baeyer
b : the mathematical ratio of the tangential frictional force per unit area to the velocity gradient perpendicular to the direction of flow of a liquid

called also coefficient of viscosity

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Examples of viscosity in a Sentence

conducted an experiment to determine the viscosity of motor oil

Recent Examples on the Web

Fluids with no viscosity at all, like superfluids, have some really weird properties. Chris Lee, Ars Technica, "Quark-gluon plasma reveals viscosity-free properties," 19 Dec. 2018 That said, coolant is important, because if your car starts running hot, then the oil has lower viscosity and doesn’t lubricate the engine as well. Popular Mechanics, "The Lightning-Fast Guide to Figuring Out What's Wrong With Your Car," 21 Nov. 2017 Secondly, the vehicle came with synthetic-blend motor oil with a 0W-20 viscosity rating. Ray Magliozzi,, "CAR TALK: Time To Trade Out Old Reliable For New Subaru?," 25 May 2018 The surface of the lava cools in both, but depending on its viscosity, the resulting rocks are very different. Maya Wei-haas, Smithsonian, "A Brief Glossary of Volcano Vocab," 25 May 2018 Volcanoes that form over land contain what's called silicic magma, which is high in silica and has a high viscosity. Sarah Gibbens, National Geographic, "No, Hawaii's Volcano Won't Trigger a Mega-Tsunami," 17 May 2018 One is that the propellers and rotors used to lift conventional aircraft are not effective at small scales, where the viscosity of air is a problem. The Economist, "The world’s lightest wireless flying machine lifts off," 15 May 2018 Basaltic magma has a low viscosity, which prevents it from piling up like the thicker magmas responsible for angrier, pointy volcanoes like Mt. St. Helens. Scott K. Johnson, Ars Technica, "Here’s what’s going on with Hawaii’s erupting volcano," 11 May 2018 This allows fluids that have thickened because of the arctic temperatures to reach proper viscosity. Luz Lazo, Washington Post, "Bitter cold bites Washington — and takes toll on drivers and their car batteries," 3 Jan. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'viscosity.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of viscosity

14th century, in the meaning defined at sense 1

History and Etymology for viscosity

Middle English viscosite, from Anglo-French viscosité, from Medieval Latin viscositat-, viscositas, from Late Latin viscosus viscous

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Learn More about viscosity

Statistics for viscosity

Last Updated

24 Dec 2018

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Time Traveler for viscosity

The first known use of viscosity was in the 14th century

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More Definitions for viscosity


vis·​cos·​i·​ty | \ vis-ˈkäs-ət-ē \
plural viscosities

Medical Definition of viscosity

1 : the quality of being viscous especially : the property of resistance to flow in a fluid or semifluid
2 : the ratio of the tangential frictional force per unit area to the velocity gradient perpendicular to the direction of flow of a liquid

called also coefficient of viscosity

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Comments on viscosity

What made you want to look up viscosity? Please tell us where you read or heard it (including the quote, if possible).


a complex dispute or argument

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