Deus

Deus (, ) is the Latin word for "god" or "deity".
Latin "deus" and "dīvus" ("divine") are in turn descended from Proto-Indo-European *"deiwos", "celestial" or "shining", from the same root as "*Dyēus", the reconstructed chief god of the Proto-Indo-European pantheon. 
In Classical Latin, "deus" (feminine "dea") was a general noun referring to a deity, while in technical usage a "divus" or "diva" was a figure who had become divine, such as a divinized emperor. In Late Latin, "Deus" came to be used mostly for the Christian God. It was inherited by the Romance languages in Galician and Portuguese "Deus", Catalan and Sardinian "Déu", French and Occitan "Dieu", Friulian and Sicilian "Diu", Italian "Dio", Spanish "Dios" and (for the Jewish God) Ladino דייו/דיו "Dio/Dyo", etc., and by the Celtic languages in Welsh "Duw" and Irish "Dia".
Cognates.
While Latin "deus" can be translated as and bears superficial similarity to Greek θεός "theós", meaning "god", these are false cognates. A true cognate is Ancient Greek Zeus, king of the Olympian gods in Greek mythology (, or ; , ). In the archaic period, the initial Zeta would have been pronounced such that Attic Ζεύς would phonetically transliterate as "Zdeús" or "Dzeús", from Proto-Hellenic "*dzéus". 
By combining a form of "deus" with the Ancient Roman word for "father" (, ), one derives the name of the mythical Roman equivalent of Zeus: the sky god "Diespiter" (), later called "Iuppiter" or Jūpiter, from Proto-Italic "*djous patēr", descended from Proto-Indo-European root "*Dyḗws*Pahtḗr" literally meaning 'Sky Father'. From the same root is derived the Greek vocative "O father Zeus" (), and whence is also derived the name of the Hindu sky god Dyáuṣ Pitṛ́ (Vedic Sanskrit: , ), and Proto-Germanic "*Tīwaz" or "Tius" hence Old Norse Týr. 
Latin Bible.
Latin "Deus" consistently translates Greek Θεός "Theós" in both the Vetus Latina and Jerome's Vulgate. In the Septuagint, Greek "Theós" in turn renders Hebrew Elohim (אֱלוֹהִים, אלהים), as in Genesis 1:1:
In theological terminology.
The word "de-us" is the root of deity, and thereby of deism, pandeism, and polydeism, all of which are theories in which any divine figure is "absent" from intervening in human affairs. This curious circumstance originates from the use of the word "deism" in the 17th and 18th centuries as a contrast to the prevailing "theism", belief in an actively intervening God:
Followers of these theories, and occasionally followers of pantheism, may sometimes refer to God as "Deus" or "the Deus" to make clear that the entity being discussed is not a theistic "God". Arthur C. Clarke picks up this usage in his novel "". William Blake said of the Deists that they worship "the Deus of the Heathen, The God of This World, &amp; the Goddess Nature, Mystery, Babylon the Great, The Druid Dragon &amp; hidden Harlot".
In Cartesian philosophy, the phrase "deus deceptor" is sometimes used to discuss the possibility of an evil God that seeks to deceive us. This character is related to a skeptical argument as to how much we can really know if an evil demon were attempting to thwart our knowledge. Another is the "deus otiosus" ("idle god"), which is a creator god who largely retires from the world and is no longer involved in its daily operation. A similar concept is that of the "deus absconditus" ("hidden god") of Thomas Aquinas. Both refer to a deity whose existence is not readily knowable by humans through either contemplation or examination of divine actions. The concept of "deus otiosus" often suggests a god who has grown weary from involvement in this world and who has been replaced by younger, more active gods, whereas "deus absconditus" suggests a god who has consciously left this world to hide elsewhere.
Latin phrases with "deus".
"Nobiscum deus" ("God with us") was a battle cry of the late Roman Empire and of the Byzantine Empire. The name "Amadeus" translates to "for love of God". The genitive/dative "dei" occurs in such phrases as Roman Catholic organization "Opus Dei" (work of God), "Agnus Dei" (Lamb of God) and "Dei Gratia" (By the Grace of God).