Nine. (three times threes or the trinity of trinities)

Nine, five, and three are mystical numbers Nine consists of a trinity of trinities. According to the Pythagorean numbers, man is a full chord, or eight notes, and deity comes next. Three, being the trinity, represents a perfect unity; twice three is the perfect dual; and thrice three is the perfect plural. This explains the use of nine as a mystical number, and also as an exhaustive plural, and consequently no definite number, but a simple representative of plural perfection. (See DIAPASON.) 1
(1) Nine indicating perfection or completion: