What is the prefix for good well?

The prefix for "good" or "well" depends on the context and the specific word you're looking to create. There isn't one single, universally applicable prefix. However, some possibilities include:

* Bene- (Latin): This prefix means "good" or "well," and is found in words like "beneficial" and "benevolent."

* Eu- (Greek): This prefix also means "good" or "well," and appears in words like "euphoria" and "euphemism."

The best prefix will depend on the specific word you want to form.