Define volume charge density and write its SI unit.

Explanation

**Step-by-Step Solution:**

1. **Definition of Volume Charge Density:**
Volume charge density is defined as the amount of electric charge per unit volume. It quantifies how much charge is distributed in a given volume of space.

2. **Mathematical Representation:**
The volume charge density is represented by the symbol \( \rho \). Mathematically, it can be expressed as:
\[
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