Fatto generale: 40 is the number of years of marriage as the ruby wedding anniversary.
Fatto matematico: 40 is the only number whose letters are in alphabetical order.
Trivia: 40 is the number of attempts needed before the creation of the "water displacing" substance in the spray WD-40.
Data storica: February 9th is the day in 1895 that William G. Morgan creates a game called Mintonette, which soon comes to be referred to as volleyball.