What is the prefix of safe?

There isn't a single prefix that directly means "safe". However, depending on the context, you might use prefixes like:

* un- (meaning "not") as in unsafe

* pre- (meaning "before" or "in advance") as in presafe (though this is less common and might refer to something like a safety check)

* re- (meaning "again") as in resafety (meaning to make something safe again)

It's important to understand the specific meaning you want to convey when choosing a prefix.