Is octopi grammatically correct?

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Tags

1. #works
2. #derives
3. #octopuses
4. #alternative
5. #people
6. #adopted
7. #edited
8. #appear
9. #octopi
10. #octopus
11. #problem
12. #rarely
13. #mistake
14. #plural
15. #greek
16. #occasionally
17. #acceptable
18. #became