What cartridge, also known as 9 mm Luger by the C.I.P. or 9 mm NATO by NATO, is used in the submachine gun the MP 40?
9×19mm Parabellum
Title: 9×19mm Parabellum
Passage: The 9×19mm Parabellum, also known as 9 mm Luger by the C.I.P. or 9 mm NATO by NATO (abbreviated 9mm, 9mmP, 9×19mm or 9×19) is a cartridge that was designed by Georg Luger and introduced in 1902 by the German weapons manufacturer Deutsche Waffen und Munitionsfabriken (DWM) (German Weapons and Munitions Factory) for their Luger semi-automatic pistol.
Title: 9×18mm Makarov
Passage: The 9×18mm Makarov (designated 9mm Makarov by the C.I.P. and often called 9×18mm PM) is a Russian pistol and submachine gun cartridge.  During the latter half of the 20th Century it was a standard military pistol cartridge of the Soviet Union and the Eastern Bloc, analogous to the 9×19mm Parabellum in NATO and Western military use.
Title: MP 40
Passage: The MP 40 ("Maschinenpistole 40") was a submachine gun chambered for the 9×19mm Parabellum cartridge.  It was developed in Nazi Germany and used extensively by the Axis powers during the Second World War.
9×19mm Parabellum MP 40