It's possible you might be thinking of the prefix "ambi-", which means "both" or "on both sides".
Here are some examples of words that start with "ambi-":
* Ambidextrous: Able to use both hands equally well.
* Ambiguous: Open to more than one interpretation; unclear.
* Ambivalent: Having mixed feelings or contradictory ideas about something.
* Ambient: Relating to the surrounding atmosphere or environment.
* Ambit: The scope or range of something.
Let me know if you were thinking of a different prefix, and I'll be happy to help!