viscosity
vih-SKOS-ih-tee
/vɪˈskɒsəti/
The state of being thick, sticky, and semi-fluid in consistency, due to internal friction within a fluid that resists flow.
In food science, viscosity determines the 'mouthfeel' of liquids, ranging from low-viscosity liquids like water to high-viscosity fluids like honey or molasses.
The story behind the word. The word 'viscosity' has a surprisingly sticky origin. It comes from the Latin 'viscum', which referred to mistletoe. Ancient Romans used to squeeze the berries of mistletoe to create a thick, sticky glue called birdlime, which they smeared on tree branches to catch small birds.
Word relationships
- thickness: Thickness is a general, everyday word, while viscosity is the precise scientific measurement of a fluid's resistance to flow.
- fluidity: The ease with which a fluid flows; a fluid with low viscosity has high fluidity.
Commonly confused with
- density: Density is mass per unit volume (how heavy something is for its size), whereas viscosity is a fluid's resistance to flow (how thick or sticky it is).
Word family
- viscous (adjective): Thick, sticky, and having a high viscosity.
Collocations
- high viscosity
- viscosity index
- measure viscosity
Example sentences
- "Reducing the stock over low heat increases its viscosity, turning it into a rich, velvety glaze that coats the back of a spoon." Describing the texture of a sauce.
- "The viscosity of honey decreases significantly as its temperature rises, making it much easier to pour." A fluid dynamics textbook.
Memory hook
Think of 'viscous' liquid as being so thick and sticky that it 'whisks' very slowly in a bowl. Whisking a thick, slow liquid.
When not to use
Do not use this to describe the density of a solid; it is strictly a property of fluids (liquids and gases).
Fun facts
- Ketchup is a non-Newtonian fluid, meaning its viscosity changes depending on how hard it is shaken or squeezed; shaking it actually lowers its viscosity, allowing it to pour.
- Maple syrup is graded partly based on its viscosity and clarity, which change depending on when the sap was harvested during the spring run.
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