viscosity

noun

vis·​cos·​i·​ty vi-ˈskä-sə-tē 

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

Synonyms

• consistency
• consistence
• thickness

Examples of viscosity in a Sentence

conducted an experiment to determine the viscosity of motor oil

Recent Examples on the Web

The model accounts for temperature-dependent properties like electrolyte viscosity and predicts voltage, ion concentrations, temperature, and power parameters. —Aman Tripathi, Interesting Engineering, 3 Sep. 2025

Lava produced by stratovolcanoes typically has a high viscosity, traveling only short distances, and pyroclastic flows — avalanches of hot gases and debris — or mudflows can kill people up to a distance of 10 to 20 kilometers (six to twelve miles). —David Bressan, Forbes.com, 31 Aug. 2025

Many industrial strategies for stabilizing foams rely on altering the viscosity; this shows those methods are ineffective. —Jennifer Ouellette, ArsTechnica, 26 Aug. 2025

By allowing droplets to move freely, the study explores how surface tension, viscosity and other forces affect fluid dynamics in microgravity. —Kenna Hughes-Castleberry, Space.com, 8 July 2025

Word History

Etymology

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

First Known Use

14th century, in the meaning defined at sense 1

Phrases Containing viscosity

• coefficient of viscosity
• viscosity index

Rhymes for viscosity

• atrocity
• ferocity
• monstrosity
• pomposity
• porosity
• precocity
• schistosity
• velocity
• verbosity
• animosity
• curiosity
• generosity

Kids Definition

viscosity

noun

vis·​cos·​i·​ty vis-ˈkäs-ət-ē 

plural viscosities

: the quality or state of being viscous

especially : the characteristic of a fluid that resists flow

an oil of high viscosity

Medical Definition

viscosity

noun

vis·​cos·​i·​ty vis-ˈkäs-ət-ē 

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