Difference between Fluid and Liquid

By: | Updated: Dec-12, 2017

Fluid and liquid sound like the same thing, right? As in “drink more fluids when you are sick” and “water is a liquid.” Then, what is the difference between the two and in what context does it matter most?

Summary Table

Fluid Liquid

A condition specific to certain substances

A phase of matter

Its essential characteristic is that it flows and has viscosity

Its essential characteristic is that it flows and has volume, but no shape

Fluids include liquids

All liquids are fluid

Definitions

water
Fluid mechanics

Fluid is a term defining the condition of a substance that deforms and flows constantly. It is a phase of matter that includes liquids, gases, plasma, and certain categories of solids made of plastic. A fluid lacks rigidity and it cannot resist sheer force when it is applied to it. Also, it flows and changes shape immediately after.

A liquid is one of the four states of matter, along with gas, solids, and plasma. This state is defined by a volume with no fixed shape. It takes the shape of the container it is placed in. Also, liquids are fluids, in the sense that they flow and do not resist force when applied to them.

Fluid vs Liquid

When you understand the difference between a fluid and a liquid, you understand why all liquids are fluids, but not all fluids are liquid.

Fluid is a condition of specific substances, whereas liquid is one of the phases of matter. The essential characteristic of fluids is that they flow. Also, when defining a fluid substance, you must also mention its viscosity. Liquids, on the other hand, flow and are defined as having volume without a fixed shape.

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