How is the 12 bar blues pattern defined?

Related questions

1. What is the difference between jazz and blues?
2. What is R&B classified?
3. Who is an R&B singer?
4. What is the 12 bar blues structure?
5. What made the blues popular?
6. Why is R&B called rhythm and blues?
7. Who is the founder of R&B?
8. What does R&B stand for now?
9. How many bars are in a verse?
10. What makes R&B R&B?

Tags

1. #fourth
2. #first
3. #blues
4. #features
5. #sequence
6. #scale
7. #typically
8. #based
9. #divided
10. #written
11. #three
12. #notes
13. #segments
14. #progression
15. #musical
16. #fifth
17. #common
18. #eight
19. #chords
20. #standard