What is pleurisy?

Explanation

**Step-by-Step Solution:**

1. **Understanding the Structure**: The lungs in humans are surrounded by a double-layered membrane known as the pleura. This structure is crucial for the protection and functioning of the lungs.

2. **Definition of Pleurisy**: Pleurisy is a medical condition that involves inflammation of the pleura, the double-layered membrane surrounding the lungs.

3. **Cause of Pleurisy**: The inflammation in the pleura can lead to various symptoms and complications. This inflammation can occur due to infections, autoimmune diseases, or other medical conditions.

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