viscosity

noun vis·cos·i·ty \ vi-ˈskä-sə-tē \

|Updated on: 11 Jun 2018

Definition of viscosity

plural viscosities

1 : the quality or state of being viscous : a sticky or glutinous consistency

2 a 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

See viscosity defined for kids

Examples of viscosity in a Sentence

conducted an experiment to determine the viscosity of motor oil

Recent Examples of viscosity from the Web

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, courant.com, "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
Not to mention, when that time of the month rolls around, the oil beneath your skin changes consistency from an olive oil type of thickness to a honey-like viscosity.

— carly cardellino, Cosmopolitan, "15 Acne-Causing Behaviors You Didn’t Even Know You Were Doing," 10 Jan. 2017

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.

Origin and Etymology of viscosity

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

NEW! Time Traveler

First Known Use: 14th century

in the meaning defined at sense 1

See Words from the same year

viscosity Synonyms

Synonyms

consistence, consistency, density, thickness, viscidity;

Related Words

compactness, firmness, solidity;

ropiness, stickiness;

Other Chemical Engineering Terms

alkali, cation, decant, hygroscopic, isotope, oxidize, slurry, solute, viscous

Medical Dictionary

viscosity

noun vis·cos·i·ty \ vis-ˈkäs-ət-ē \

medical Definition of viscosity

plural viscosities

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