What is the Greek word for diligence?

There isn't one single perfect Greek word for "diligence" as the concept can be expressed through several words depending on the nuance. However, some good options include:

* Σπουδή (spoudē): This word implies earnest effort, zeal, and diligence, often in the pursuit of a goal. It's probably the closest single word.

* Επιμέλεια (epiméleia): This translates more specifically to "care," "attention," or "carefulness," which are components of diligence.

* Φροντίδα (phrontida): Similar to *epiméleia*, this word signifies care and attention, but can also imply foresight and planning.

The best word to use would depend on the context. If you can provide the context in which you need the word, I can help you choose the most appropriate one.