Here's why:

* Fluids: Fluids are substances that can flow. This includes liquids and gases.

* Particle Movement: The particles in fluids are not rigidly fixed in a lattice structure like solids. They have the ability to move freely and slide past each other.

* Weak Intermolecular Forces: The forces of attraction between particles in fluids are weaker than those in solids. This allows particles to move past each other more easily.

Examples:

* Water: Water molecules can flow over each other, allowing it to be poured and take the shape of its container.

* Air: Air molecules can flow around objects, creating wind.

In contrast, solids have strong intermolecular forces that hold particles in fixed positions, preventing them from flowing over each other.