Word Choice – Fluids vs. Liquids Explained

meaningword-choice

What is the difference between fluid and liquid?

I'm thinking of this in the context of drink plenty of fluids.

Best Answer

A fluid can either be a liquid or a gas; as such, fluid is a hypernym of liquid in this regard. In your example

Drink plenty of fluids

it's only idiomatic to use fluids instead of liquids. (I wonder what else could be drunk besides a liquid/fluid, anyway!) You also hear things like:

Your body needs lots of fluids

In day-to-day usage, one will find liquid only used when the state of matter of a substance is in question or important to note. For example:

"How's the brownie mix looking?" "It's still basically liquid!"

When ice-cream is involved, melted is more likely to be used instead of liquid. One may also find liquid used in a financial context:

They think I'm liquid but, man, I'm flat broke!

Fluid just sounds smoother and it rolls off the tongue much easier. That probably explains why it's more commonly used in place of liquid. People would probably use gas if they wanted to be specific. Here are some common idiomatic phrases:

  • body fluids
  • engine fluid
  • transmission fluid
  • poisonous liquid
  • hot liquid
  • toxic fluid[s]
  • liquid coolant
  • cooling fluid

From the above examples, you may notice that fluid tends to be used for a liquid substance that has a specified/particular purpose. Thus, transmission liquid would be unidiomatic, for instance.