The god's name in the nominative is Ζεύς Zeús. It is inflected as follows: vocative: Ζεῦ Zeû; accusative: Δία Día; genitive: Διός Diós; dative: Διί Dií. Diogenes Laertius quotes Pherecydes of Syros as spelling the name, Ζάς.
Zeus is the Greek continuation of *Di̯ēus, the name of the Proto-Indo-European god of the daytime sky, also called *Dyeus ph2tēr ("Sky Father"). The god is known under this name in the Rigveda (Vedic Sanskrit Dyaus/Dyaus Pita), Latin (compare Jupiter, from Iuppiter, deriving from the Proto-Indo-European vocative *dyeu-ph2tēr), deriving from the root *dyeu- ("to shine", and in its many derivatives, "sky, heaven, god"). Zeus is the only deity in the Olympic pantheon whose name has such a transparent Indo-European etymology.
The earliest attested forms of the name are the Mycenaean Greek 𐀇𐀸, di-we and 𐀇𐀺, di-wo, written in the Linear B syllabic script.
Plato, in his Cratylus, gives a folk etymology of Zeus meaning "cause of life always to all things," because of puns between alternate titles of Zeus (
Zen and Dia) with the Greek words for life and "because of." This etymology, along with Plato's entire method of deriving etymologies, is not supported by modern scholarship.