What defines an event horizon?

Related questions

1. Is a black hole dark matter?
2. How heavy is a black hole?
3. What's beyond the observable universe?
4. Who survived the Deepwater Horizon?
5. Do all black holes have the same density?
6. What happens in Event Horizon?
7. Do black holes have infinite density?
8. What is inside a black hole?
9. What happens if you enter a black hole?
10. Do wormholes exist?

Tags

1. #other
2. #velocity
3. #horizon
4. #which
5. #exceeds
6. #black
7. #region
8. #words
9. #defining
10. #speed
11. #nothing
12. #space
13. #boundary
14. #escape
15. #object
16. #event
17. #within
18. #light
19. #around