In Greek mythology, Dionysus was the Greek god of wine and fertility. The name Dionysus can also be spelled as Dionysos and is also known as Bacchus.
The origin of the name Dionysus is unknown, but it is hypothesized that "Dio" comes from the genitive form of "Zeus", which means "god" or "divinity". The second part "nysos", may derive from Mount Nysa, which was where Dionysus was born.
The correct pronunciation of Dionysus in English is Dye-uh-NYE-sus. The most important part of this pronunciation to keep in mind is that the "ny" part is pronounced as -NYE and not as -nee. It is also important to note that the stress falls on that same third syllable.