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 of viscosity

• 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 same engine used in the RAV4 in some markets, including Mexico, is approved for oil viscosities ranging from 0W-16 to 10W-30, provided the oil meets the appropriate SM/SN API (American Petroleum Institute) service classification. — John Paul Senior Manager Public Affairs and Traffic Safety Aaa Northeast, Hartford Courant, 19 Sep. 2026

The engine protectant does not change the oil viscosity, which is a good thing, and it is designed to reduce friction. — John Paul, The Providence Journal, 11 Sep. 2026

Both flavors lend beverages a complex mouthfeel or viscosity. — Randi Gollin, Martha Stewart, 11 Sep. 2026

The equations must produce their own breakdown despite viscosity, which normally smooths violent changes in fluid motion. — Aamir Khollam, Interesting Engineering, 8 Sep. 2026

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