Many people ask about my name. Is it Yannis, Ioannis, John, Giannis, Yiannis?

According to wikipedia: "Yannis or Yiannis or Giannis is a common Greek name, a variant of John (Hebrew) meaning "the Lord is gracious." Variants include Ioannis, Yanni, Iannis and Yannakis.".

- http://en.wikipedia.org/wiki/Yannis (in this link you can see other variants also like Giannis)

According to www.behindthename.com:

Yannis is a variant for Yiannis. Yiannis and Ioannis are the greek forms of John, which in turn stems from the latin form of the greek name Ioannes.

The pronunciation of Yannis and Yiannis are the same. The same for Ioannis and Ioannes.

Ioannis is a formal version of the name, being used mostly in formal documents. In everyday life, people mostly use the name Yannis.

More interesting things about Greek letters and alphabet

In Ioannis the "I" is pronounced as "E". That is why Ioannis and Ioannes sound the same!

"I" is the greek letter Yiota or Iota, which was later taken by Romans and represented "i". However the pronunciation changed from "e" to "i".

What is new in that? Well the greek letters that are used in math, logic, etc are not pronounced as "i" but as "e". For example the letter φ is not "phi", but rather "phe".