What is the prefix for turst?

There is no prefix for "trust." The word "trust" is a root word on its own.

However, there are related words with prefixes that might be what you're thinking of:

* Distrust - meaning to lack confidence in someone or something

* Mistrust - meaning to have a lack of faith or confidence in someone or something

* Untrustworthy - meaning not able to be trusted

Let me know if you have any other words you'd like to find the prefixes for!