Who was Tammuz and what does he have to do with Adonis the Greek God?

The Greek Adonis, the Babylonian Tammuz, the Sumerian Dumuzi, and the Egyptian Osiris are all forms of the same god.

After being carried off to the underworld, Tammuz, god of crops and vegetation, was rescued by his lover Ishtar.

All life on earth withered between his dying (in winter) and his rising (in spring).