In classical fluid mechanics, a fluid is said to behave as a continuum. in this context, continuum means:

In classical fluid mechanics, a fluid is said to behave as a continuum. in this context, continuum means: that the fluid itself is made up of a continuous mass that has readily identifiable properties at any and every point in the mass.
This makes the particles in fluid became less restricted, making them able to fill in every shape of medium that it put in.

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