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Dyēus (also *Dyēus ph2ter) is believed to have been chief deity in the religious traditions of the prehistoric Proto-Indo-European tribes. Part of a larger pantheon, he was the god of the daylight sky, and his position may have mirrored the position of the patriarch or monarch in society. This deity is not directly attested; rather scholars have reconstructed this deity from the languages and cultures of later Indo-European nations.
Later gods etymologically connected with Dyeus 
- In Greek mythology Zeus
- In Roman mythology Jupiter (originally Iuppiter)
- In Historical Vedic religion Dyauṣ Pitār
- Possibly Dionysus, and Thracian Sabazios (from Saba Zeus?)
Rooted in the related but distinct Indo-European word *deiwos is the Latin word for deity, deus. The Latin word is also continued in English divine, "deity", and the original Germanic word remains visible in "Tuesday" ("Day of Tīwaz") and Old Norse tívar, which may be continued in the toponym Tiveden ("Wood of the Gods", or of Týr).
Deiwos group 
- Germanic Tiwaz (later known as Týr)
- Latin Deus
- Indo-Iranian Deva/Daeva
- Baltic Dievas
- Celtic mythology e.g. Gaulish Dēuos
- Possible Slavic mythology divu (demons — meaning acquired from Iranian)
Dyeus was addressed as Dyeu Ph2ter, literally "Sky father" or "shining father", as reflected in Latin Iūpiter, Diēspiter, possibly Dis Pater and deus pater, Greek Zeu pater, Sanskrit Dyàuṣpítaḥ. In his aspect as a father god, his consort was Pltwih2 Mh2ter, "Earth Mother".
As the pantheons of the individual mythologies related to the Proto-Indo-European religion evolved, attributes of Dyeus were sometimes redistributed to other deities. In Greek and Roman mythology, Dyeus remained the chief god, but in Vedic mythology, the etymological continuant of Dyeus became a very abstract god, and his original attributes, and his dominance over other gods, were transferred to gods such as Agni or Indra.
As an ordinary noun 
Dyēus's name also likely means "the daytime sky":
- In Sanskrit as div- (nominative singular dyāus with vrddhi), its singular means "the sky" and its plural means "days".
- Pronounced *di-ēus (2 syllables) it became Latin diēs = "day".
- Finnish taivas and Estonian taevas, meaning "heaven" or "sky," are likely rooted in either neighboring Baltic Dievas or Germanic Tiwaz.