C1noun2K

Fluid

UK /["/ˈfluːɪd/"]/US /["/ˈfluːɪd/"]/

Definition

a liquid; a substance that can flow

In simple words: A substance that can flow, like liquid or gas.

Examples

  • body fluids *(= for example, blood)*
  • The doctor told him to drink plenty of fluids.
  • cleaning fluid
  • It's important to replace fluids and salts that are lost during exercise.
  • Retaining excess fluid could be a problem.
  • They drained a lot of fluid from his lungs.

Usage notes

Used to describe things that can change shape easily, such as water or air. In contexts about movement or flexibility, it's appropriate. Avoid using it in very formal writing without defining.

Grammar pattern

standalone adjective

Memory hint

Think of 'fluid' as 'flowing' — imagine water smoothly running down a stream.

Collocations

  • excess
  • amniotic
  • bodily
  • drain
  • drink
  • lose

Synonyms

  • liquid
  • flowing
  • smooth
  • mutable
  • unfixed

Antonyms

  • solid
  • rigid
  • stiff

Common mistakes

  • Confused with 'fluent' in the context of language.
  • Using 'fluid' as a noun without specifying the type, e.g. 'the fluid is...' instead of 'the fluid is water.'
  • Misunderstanding the word as only referring to liquids.