fluid

From Middle English fluid, from Latin fluidus (“flowing; fluid”), from Latin fluō (“to flow”), from Proto-Indo-European *bʰleh₁- (“to swell; surge; overflow; run”). Akin to Ancient Greek φλύειν (phlúein, “to swell; overflow”). Not related to English flow, which is a native, inherited word from *plew-.

• IPA^(key): /ˈfluːɪd/, /ˈflɪu̯ɪd/
• (obsolete) IPA^(key): /ˈfljuːɪd/[1]

• Audio (US)

  (file)

• Rhymes: -uːɪd

fluid (countable and uncountable, plural fluids)

1. Any substance which can flow with relative ease, tends to assume the shape of its container, and obeys Bernoulli's principle; a liquid, gas or plasma.
   • 2013 March, Frank Fish, George Lauder, “Not Just Going with the Flow”, in American Scientist‎, volume 101, number 2, archived from the original on 1 May 2013, page 114:

     An extreme version of vorticity is a vortex. The vortex is a spinning, cyclonic mass of fluid, which can be observed in the rotation of water going down a drain, as well as in smoke rings, tornados and hurricanes.

2. A liquid (as opposed to a solid or gas).
   • 1992, Christopher G. Morris, Academic Press, Christopher W. Morris, Academic Press Dictionary of Science and Technology, Gulf Professional Publishing, →ISBN, page 854:

     fluid inclusion Petrology, a tiny fluid- or gas-filled cavity in an igneous rock. 1-100 micrometers in diameter, formed by the entrapment of a fluid, typically that from which the rock crystallized.

   • 1995, David Kemper, Michael Piller, “Time and Again”, in Star Trek: Voyager, season 1, episode 4, spoken by The Doctor and Kes (Robert Picardo and Jennifer Lien):

     The Doctor: Get a good night's sleep and drink plenty of fluids. / Kes: Fluids? / The Doctor: Everybody should drink plenty of fluids.

   • 2006, Jörg Fitter, Thomas Gutberlet, Neutron Scattering in Biology: Techniques and Applications, Springer Science & Business Media, →ISBN, page 236:

     For studying interfaces between solid and another solid, fluid, or gas, a sample can be oriented with its reflecting surface(s) vertical (and with the scattering plane, as defined by nominal incident and reflected wavevectors, horizontal).

   • 2011, Andrew T Raftery, Michael S. Delbridge, Marcus J. D. Wagstaff, Churchill's Pocketbook of Surgery, International Edition E-Book, Elsevier Health Sciences, →ISBN, page 11:

     Tenderness: is the lump tender?
     Composition: is the mass solid, fluid or gas?

   • 2012, Will Pettijohn P.E.C., Oil & Gas Handbook: A Roughneck's guide to the Universe, AuthorHouse, →ISBN, page 23:

     The choke manifold then expels the fluid or gas to the gas buster or a panic line. The panic line will then either send the fluid or gas to the reserve pit or a flare stack or flare tank.

   • For more quotations using this term, see Citations:fluid.
3. (specifically, medicine, colloquial, typically in the plural) Intravenous fluids.

fluid (comparative more fluid, superlative most fluid)

1. (not comparable) Of or relating to fluid.
2. In a state of flux; subject to change.
   • 2013 August 3, “Boundary problems”, in The Economist, volume 408, number 8847:

     Economics is a messy discipline: too fluid to be a science, too rigorous to be an art. Perhaps it is fitting that economists’ most-used metric, gross domestic product (GDP), is a tangle too. GDP measures the total value of output in an economic territory. Its apparent simplicity explains why it is scrutinised down to tenths of a percentage point every month.

3. Moving smoothly, or giving the impression of a liquid in motion.
4. (of an asset) Convertible into cash.
5. (rare) Genderfluid.
   • 2017, Rick Riordan, Magnus Chase and the Hammer of Thor (→ISBN), page 274 (the genderfluid character Alex Fierro is speaking):

     “Oh, Loki made sure of that. My mortal parents blamed him for the way I was, for being fluid.”

   • 2021 April 24, Adrian Horton, “‘The uprisings opened up the door’: the TV cop shows confronting a harmful legacy”, in The Guardian‎, →ISSN:

     As do renewals in genres such as romcoms and teen movies, which have updated sexist, heteronormative tropes to reflect audiences’ fluid, inclusive, queer realities.

• (of or relating to fluid): fluidical, liquid; see also Thesaurus:fluidic
• (subject to change): unstable, variable; see also Thesaurus:changeable
• (moving smoothly): fluent, fluxive; see also Thesaurus:flowing or Thesaurus:runny

• fluctuate
• fluctuation
• fluency
• fluent
• flux
• fluidal
• fluidic
• fluidics
• fluidify
• fluidise
• fluidize
• fluidity
• fluidous
• semifluid

• “fluid”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.
• “fluid”, in The Century Dictionary […], New York, N.Y.: The Century Co., 1911, →OCLC.
• “fluid”, in OneLook Dictionary Search.

Borrowed from Latin fluidus.

• IPA^(key): (Central, Balearic, Valencian) [ˈflujt]

fluid (feminine fluida, masculine plural fluids, feminine plural fluides)

1. fluid

   Synonym: fluent

2. (figurative) fluid, fluent, smooth

   estil fluid ― fluid style

• fluïdesa
• superfluid

• fluir
• fluïditat

fluid m (plural fluids)

1. fluid

• fluïditzar

• fluídica

• “fluid” in Diccionari de la llengua catalana, segona edició, Institut d’Estudis Catalans.
• “fluid”, in Gran Diccionari de la Llengua Catalana, Grup Enciclopèdia Catalana, 2024
• “fluid” in Diccionari normatiu valencià, Acadèmia Valenciana de la Llengua.
• “fluid” in Diccionari català-valencià-balear, Antoni Maria Alcover and Francesc de Borja Moll, 1962.

fluid (strong nominative masculine singular fluider, not comparable)

1. fluid

   Synonym: flüssig

   • 2021 April 13, Stefan Reinecke, “Debatte um Normalität: Das Normale ist flüssig geworden”, in Die Tageszeitung: taz‎, →ISSN:

     Normalität ist nichts Statisches mehr, sie ist mobil, fluide, dehnbar. Wir brauchen sie, aber ohne Ausrufezeichen. Wahrscheinlich ist sie nur als Zwiespältigkeit zu haben.

     (please add an English translation of this quotation)

• “fluid” in Duden online
• “fluid” in Digitales Wörterbuch der deutschen Sprache

fluid n (definite singular fluidet, indefinite plural fluid or fluider, definite plural fluida or fluidene)

1. a fluid

• væske

• fluidmekanikk

• “fluid” in The Bokmål Dictionary.

fluid n (definite singular fluidet, indefinite plural fluid, definite plural fluida)

1. a fluid

• væske

• fluidmekanikk

• “fluid” in The Nynorsk Dictionary.

Borrowed from French fluide, from Latin fluidus.

fluid m or n (feminine singular fluidă, masculine plural fluizi, feminine and neuter plural fluide)

1. fluid

• fluiditate

• IPA^(key): /flûiːd/
• Hyphenation: flu‧id

flȕīd m (Cyrillic spelling флу̏ӣд)

1. fluid

fluid

1. second-person plural imperative of fluir