20 common suffixes in English are:

1. -able: Capable of (e.g., comfortable, readable)
2. -al: Relating to (e.g., seasonal, annual)
3. -ance: State or quality of (e.g., guidance, tolerance)
4. -ence: State or quality of (e.g., difference, independence)
5. -ation: Action or process of (e.g., celebration, education)
6. -ible: Capable of (e.g., divisible, flexible)
7. -ion: Action or process of (e.g., confusion, audition)
8. -ment: State or result of (e.g., enjoyment, movement)
9. -ness: State or quality of (e.g., happiness, kindness)
10. -ship: State or quality of (e.g., friendship, leadership)
11. -ful: Full of (e.g., beautiful, helpful)
12. -less: Without (e.g., careless, hopeless)
13. -ous: Full of (e.g., courageous, glorious)
14. -ly: In a manner (e.g., quickly, happily)
15. -er: One who does (e.g., teacher, player)
16. -or: One who does (e.g., actor, advisor)
17. -ist: One who is (e.g., artist, scientist)
18. -ism: Belief or practice (e.g., communism, feminism)
19. -ward: Toward (e.g., forward, backward)
20. -wise: In a manner (e.g., likewise, otherwise)