* "Definitely" is already a complete word. It means "without any doubt" or "for sure." Adding a prefix would change the meaning and create an entirely different word.
* The root word "definite" already has a prefix. The prefix "de-" means "away from" or "opposite of." Adding another prefix would make the word unnecessarily complex.
If you're looking to modify the meaning of "definitely," you could use synonyms like:
* Absolutely
* Certainly
* Positively
* Unquestionably
* For sure
Or you could use phrases to express degrees of certainty:
* Almost definitely
* Highly likely
* Very probably
* It's likely that...
Let me know if you'd like help finding synonyms for "definitely" in a specific context!