1. Absolutely
2. Unquestionably
3. Assuredly
4. Absolutely
5. Surely
6. Positively
7. Plainly
8. Decidedly
9. Obviously
10. Unequivocally
11. Indubitably
12. Undeniably
13. Manifestly
14. Veritably
15. Categorically
16. Unconditionally
17. Without a doubt
18. Unmistakably
19. Inarguably
20. Definite
21. Unquestionable
22. Verily
23. Explicitly
24. Conclusively
25. Emphatically
26. Unambiguously
27. Undoubtedly
28. Irrefutably
29. Definitively
30. Affirmatively

When searching for another word for “certainly”, there are many great options to choose from. The best ideas are those that are most appropriate for the context in which they are used. Synonyms for “certainly” can range from the more casual “absolutely” to the more formal “categorically”. Other words for “certainly” include “unquestionably”, “decidedly”, “obviously”, and “unequivocally”. For a more comprehensive list, one can look to “absolutely”, “surely”, “positively”, “plainly”, and “indubitably”. All of these words provide an accurate description of the certainty that is being expressed. No matter what the context, there is a synonym for “certainly” that will fit the situation perfectly.