What is the prefix for prefix?

This is a bit of a tricky question! There isn't a standard prefix for the word "prefix".

Here's why:

* Prefixes are already the smallest unit. Prefixes are attached to the beginning of words to change their meaning. They can't be broken down further.

* "Pre" itself is a prefix. It means "before" or "in advance of".

So, while there's no specific prefix for "prefix", you could say that "pre-" is the prefix of "prefix".