Define energy density?

Explanation

**Step-by-Step Solution:**

1. **Definition of Energy Density**: Energy density is defined as the amount of energy stored in a given system or region per unit volume. In the context of elastic materials, it refers specifically to the elastic energy stored in the material.

2. **Elastic Energy Density**: The elastic energy density can be expressed mathematically as the elastic energy stored per unit volume. This is given by the formula:
\[ \text{Elastic Energy Density} = \frac{\text{Elastic Energy}}{\text{Volume}} \]
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