Define the following and give their values in a normal human adult
Expiratory reserve volume

Explanation

### Step-by-Step Solution:

1. **Definition of Expiratory Reserve Volume (ERV)**:
- Expiratory Reserve Volume is defined as the amount of air that can be forcibly exhaled from the lungs after the end of a normal tidal expiration. It represents the extra volume of air that can be expelled beyond the normal breath.

2. **Measurement of ERV**:
- The volume of air in the lungs, including the ERV, is typically measured using a device called a spirometer. This device helps assess lung function and can provide various lung volume measurements.

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