What is the difference between yanni and yannis?

Answer 1

The difference between "Yanni" and "Yannis" lies in their grammatical function and usage. "Yanni" is the anglicized version of the Greek name "Γιάννης" (Yiannis), typically used as a given name. "Yannis" is the genitive form of "Yiannis" in Greek, indicating possession or association with Yannis. In English, "Yanni" is commonly used as a standalone name, while "Yannis" is less frequently used and usually appears in contexts where possession or association is relevant.

Answer 2

'Yanni' is used when addressing the person; 'Yannis' is used when referring to the person.

So you might say, 'Hi, Yanni!' because you're talking to him. But when talking about him you would say, 'Hey, you'll never guess what Yannis did last night at the Vicar's house!'

The appearing and disappearing 's' is fairly common in Greek names, I believe.