fluid

American  

[floo-id] / ˈflu ɪd /

noun

• fluids
  plural

1. a substance, as a liquid or gas, that is capable of flowing and that changes its shape at a steady rate when acted upon by a force tending to change its shape.

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adjective

1. pertaining to a substance that easily changes its shape; capable of flowing.

2. consisting of or pertaining to fluids.

3. changing readily; shifting; not fixed, stable, or rigid.

   fluid movements.

4. convertible into cash.

   fluid assets.

fluid British  

/ ˈfluːɪd /

noun

1. a substance, such as a liquid or gas, that can flow, has no fixed shape, and offers little resistance to an external stress

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adjective

1. capable of flowing and easily changing shape

2. of, concerned with, or using a fluid or fluids

3. constantly changing or apt to change

4. smooth in shape or movement; flowing

fluid Scientific  

/ flo̅o̅′ĭd /

1. A state of matter, such as liquid or gas, in which the component particles (generally molecules) can move past one another. Fluids flow easily and conform to the shape of their containers.

2. See also state of matter viscosity

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fluid Cultural  

1. In physics, a substance that flows — usually a liquid or a gas.

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Synonym Usage

See liquid.

Other Word Forms

Derived Forms

• fluidness
  noun
• nonfluid
  noun
• fluidal
  adjective
• unfluid
  adjective
• fluidally
  adverb
• fluidly
  adverb
• nonfluidly
  adverb

Inflected Forms

Nouns

• fluids
  plural

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Etymology

Origin of fluid

First recorded in 1595–1605; from Latin fluidus, equivalent to flu(ere) “to flow” + -idus adjective suffix; see -id ⁴

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Explanation

Something that is unstable or subject to change can be described as fluid. The fluid political situation in a particular country makes it unsafe to travel there, with the constant possibility of a violent uprising. A liquid is a fluid — something that flows easily when poured — although gases can also be called fluid. When your doctor told you to drink lots of fluids to help your cold symptoms, she probably meant things like water or orange juice, not root beer floats. If a movement is smooth, it can also be described as fluid. You have to make fluid arm movements in ballet so you look graceful.

Example Sentences

See Examples For:

fluid fluids

The scan found a hole in the mitral valve in Danny's heart, and it was also discovered he had developed sepsis, external and there was fluid in his lungs.

From BBC ● Nov. 9, 2026

As a result, a procedure to drain fluid from Isaac's brain did not take place.

From BBC ● Nov. 7, 2026

Macklem cited fluid developments in the Middle East and Canada-U.S. trade relations as sources of uncertainty.

From The Wall Street Journal ● Nov. 3, 2026

Sodium and potassium are essential minerals that help regulate fluid balance, nerve signaling, and muscle function.

From Science Daily ● Nov. 2, 2026

Time went quickly like this, moving as fluid.

From "The Marrow Thieves" by Cherie Dimaline

Health workers and carers can face a higher risk of Ebola infection because caring for infected patients may bring them into contact with blood and other bodily fluids.

From BBC ● Oct. 20, 2026

Pimple patches containing a gel called hydrocolloid can absorb fluids from oozing pimples and stop you from picking at them.

From Los Angeles Times ● Oct. 13, 2026

If the viscosity of those fluids changed too much, these processes could become severely disrupted.

From Science Daily ● Oct. 11, 2026

She was found clinging to a tree in late September and tranquilised by a rescue team who administered oxygen and intravenous fluids before moving her to the rehabilitation centre.

From Barron's ● Oct. 9, 2026

Blaise Pascal was enthralled, and started performing experiments of his own, using water, wine, and other fluids.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife

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Related Words

• flexible
• shifting
• unsettled
• unstable

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