What is the prefix for express?

There isn't a single, universally accepted prefix for "express". However, depending on the context, some common prefixes include:

* Ex-: This prefix is used to emphasize the act of sending or taking something out or away, as in "express train" or "express mail".

* Super-: This prefix can be used to indicate something that is faster, more intense, or more powerful, as in "super express" or "express superhighway".

* Ultra-: This prefix is similar to "super-" and signifies something that is extremely fast or efficient.

The best prefix to use will depend on the specific meaning you want to convey.