Define arthritis.

Explanation

### Step-by-Step Solution to Define Arthritis

1. **Definition of Arthritis**:
- Arthritis is a medical condition characterized by inflammation of the joints, which leads to pain and discomfort.

2. **Symptoms**:
- The primary symptom of arthritis is joint pain, which can be accompanied by swelling, stiffness, and reduced range of motion in the affected joints.

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