What is the word evangelism in Greek?

The word "evangelism" doesn't have a single perfect equivalent in classical Greek, as the concept developed within the context of early Christianity. However, the closest related words and phrases would be based on the Greek word εὐαγγέλιον (euangelion), which means "good news."

Therefore, depending on the nuance you want to convey, you could use:

* εὐαγγελισμός (euangelismos): This is the most direct translation, meaning "the proclamation of the good news" or "the act of evangelizing." This is probably the closest single-word equivalent.

* κηρυγμα εὐαγγελίου (kerygma euangeliou): This translates to "proclamation of the gospel" and emphasizes the public preaching aspect. `Kerygma` refers to a proclamation or preaching.

So, while there's no perfect one-to-one translation, εὐαγγελισμός (euangelismos) is the most accurate and commonly used term.