viscosity
vis-KOSS-uh-tee
/vɪˈskɒs.ə.ti/
The state of being thick, sticky, and semi-fluid in consistency, due to internal friction.
Specifically measures a fluid's internal resistance to flow; honey has high viscosity, while water has low viscosity.
The story behind the word. Ancient Romans crushed mistletoe berries to create a sticky, gooey adhesive called birdlime, which they smeared on branches to trap small birds. This sticky substance, known as 'viscum', became the root of our modern word for a fluid's resistance to flow.
Word relationships
- thickness: Thickness is a general term, whereas viscosity is a precise scientific measure of internal friction.
- stickiness: Stickiness refers to adhesion to other surfaces, while viscosity is internal resistance to flow.
- fluidity: Fluidity is the ease with which a substance flows, the exact mathematical inverse of viscosity.
Commonly confused with
- density: Density is mass per unit volume, whereas viscosity is resistance to flow; oil is less dense than water but far more viscous.
Word family
- viscous (adjective): Thick, sticky, and having a high resistance to flow.
Collocations
- high viscosity
- low viscosity
- dynamic viscosity
- measure viscosity
Example sentences
- "The viscosity of the motor oil increases significantly in freezing temperatures, making it harder to start the engine." Scientific observation of fluid behavior
- "In the famous pitch drop experiment, the viscosity of pitch was proven to be roughly 230 billion times that of water." Classic scientific experiment
Memory hook
Think of 'viscous' liquid as being 'visibly cautious' as it crawls slowly down a slope. Viscous = Visibly Cautious flow.
When not to use
Do not use to describe solid stickiness like tape or glue unless referring to their fluid state before drying.
Fun facts
- The pitch drop experiment, started in 1927 to measure the viscosity of pitch, has only dropped nine times in nearly a century.
Take your vocabulary further with LangBlitz
Our English vocabulary app: FSRS spaced repetition, 5,000+ curated words across 119 topic groups, CEFR A1 to C2. Explore your mastery with the beautiful Vocabulary World feature.