Here's a breakdown:

* Closely packed: The particles in a solid are very close to each other, with very little space between them. This is why solids have a definite shape and volume.

* Regular pattern: The particles are arranged in a specific, repeating pattern, like a grid. This pattern is what gives solids their crystalline structure.

Think of it like this: Imagine building a wall with bricks. The bricks are like the particles in a solid. They are tightly packed together and arranged in a specific pattern, giving the wall its structure and strength.

Here are some key characteristics of solids due to their particle arrangement:

* Definite shape: Solids maintain their shape because the particles are fixed in their positions.

* Definite volume: Solids have a definite volume because their particles are tightly packed together.

* Incompressibility: Solids are difficult to compress because their particles are already very close together.

* Rigidity: Solids are rigid because their particles are fixed in place, making them resistant to deformation.

While many solids exhibit this perfect crystalline structure, some are amorphous. This means their particles lack a regular, repeating pattern. Examples include glass and rubber.