What is the prefix for adventure?

There isn't a specific prefix for "adventure." However, there are words that start with "ad-" that relate to the concept of adventure, such as:

* Adventitious: Happening by chance or unexpectedly.

* Adventurous: Willing to try new and exciting things.

* Adventurer: Someone who enjoys exciting or dangerous experiences.

If you're looking for a prefix that specifically relates to exploring or going on a journey, "ex-" could be considered, as in "explore" or "expedition."