(n): an amount of time
(n): (New Testament) in Revelations it is foretold that those faithful to Jesus will reign with Jesus over the earth for a thousand years; the meaning of these words have been much debated; some denominations (e.g. Jehovah's Witnesses) expect it to be a thousand years of justice and peace and happiness
(n): a belief (or system of beliefs) accepted as authoritative by some group or school
(n): the 1000th anniversary (or the celebration of it)
(n): the date on which an event occurred in some previous year (or the celebration of it)