Explain how polymorphism + inheritance together enable extensibility.

1. Start with a clear definition, then explain where the concept appears in real systems.

2. Add one practical example so the answer sounds interview-ready instead of memorized.

3. Close with trade-offs, edge cases, and the mistake candidates usually make.

• Include one concise example and one common interview caveat.
• Keep the answer structured enough to revise quickly before a technical screen.