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Definition of fluid
fluid
/ˈfluː.ɪd/
flu · id
Adverb:fluidly
•Plural:fluids
fluid Lexical Profile
CEFR
B2
Grade
5
Tier
2
Usage
Top 5k
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Scrabble US
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WWF
Wordle Guess
• noun
1
A substance that has no fixed shape and yields easily to external pressure, primarily encompassing liquids and gases.
Example
"The mechanical engineer tested the fluid to determine its viscosity under extreme temperature conditions."
2
A liquid produced by or secreted within a living organism.
Example
"The doctor advised the patient to drink plenty of fluids to stay properly hydrated during the recovery."
Synonyms
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View all antonyms for fluidWord Origin & Etymology
From Latin 'fluidus' meaning 'flowing' or 'soft', derived from the verb 'fluere' (to flow).
Usage Trend
Historical frequency of usage in published text.
180019102020
Data source: Google Books Ngram Viewer
Cite this Entry
Wordmom. (2026). Definition of Fluid. In Wordmom Dictionary. Retrieved Oct 16, 2026, from https://wordmom.com/dictionary/fluid