40
40 or forty commonly refers to: 

40 (number)
The years 40 BC and AD 4040 or forty may also refer to:

Music
40 (record producer) (born 1983), Canadian hip hop producer (born Noah Shebib)
Forty (album), a 2001 live album by Thomas Dolby
40 (Foreigner album), 2017
40 (Stray Cats album), 2019
40 (Sunnyboys album), 2019
40 (Grupo Niche album), 2020
40, an album by Peter Morén
40 (concert video), by the Allman Brothers Band
"40" (song), by U2
"40'", a song by Franz Ferdinand from Franz Ferdinand, 2004
"Forty", a song by Karma to Burn from Almost Heathen, 2001

Films
This Is 40, a 2012 American film

Other uses
40 ounce or forty, a bottle of malt liquor
Forty winks or forty, sleep or nap
.40 S&W, pistol cartridge
.40 Super, wildcat pistol cartridge
(, the ASCII character with code 40

See also
Tessarakonteres (English: Forty), a very large ancient Egyptian galley
Top 40: a radio format; the current, 40 most-popular songs in the music industry