Hades (from Greek Άδης, Haidēs, originally Άιδης, Haidēs or Άΐδης, Aidēs, probably from Indo-European *n̥-wid- 'unseen') refers to both the ancient Greek underworld and the god of the dead. The word originally (as in Homer) referred to just the god; Άδού, Haidou its genitive, was an elision of "the house of Hades". Eventually, the nominative, too, came to designate the abode of the dead.
Hades and his brothers Zeus and Poseidon defeated the Titans and claimed rulership over the universe, ruling the underworld, sky, and sea, respectively. Hades is depicted as a grim figure.
Hades was also known as Pluto (from Greek Ploutōn), and was known by this name, as "the unseen one", or "the rich one", as well as Dis Pater and Orcus, in Roman mythology; the corresponding Etruscan god was Aita. The symbols associated with him are sceptre and cornucopia.
The term hades has sometimes been used in Christianity to mean the abode of the dead, where the dead would await Judgment Day either at peace or in torment. See Hades in Christianity.