1) Hell is the place of the future punishment call "Gehenna" or "Gehenna of fire". This was originally the valley of Hinnom, south of Jerusalem, where the filth and dead animals of the city were cast out and burned; a fit symbol of the wicked and their future destruction.
Part of Speech: noun feminine
Citing in TDNT: 1:657, 113
Of Hebrew origin ([H1516] and [H2011]); valley of (the son of) Hinnom; gehenna (or Ge-Hinnom), a valley of Jerusalem, used (figuratively) as a name for the place (or state) of everlasting punishment: - hell.
These two sites give similar information, with the definition from several dictionaries and statistics on the use of the word.
Perseus Digital Library
University of Chicago's Logion lexicon
Thayer's dictionary plus other information.
From this site's dictionary (in Italian)
Click on the first column to search for that word as a form of the root γέεννα; click on the second column to search for that grammatical form of the root γέεννα; click on the third column to search for that word and grammatical form; click on the total to search for the root γέεννα.