9mm IS the caliber. If you mean what is it equivalent to, it is approximately the same as a .38.
No
Yes you can.
No, you cannot.
the are also chambered for the 38 caliber, 9mm caliber and 22 caliber
The .380 caliber is typically a pistol cartridge, also known as 9mm Short or 9mm Kurz, while the .38 caliber is a revolver cartridge, usually referring to .38 Special or .38 S&W. The .380 cartridge is generally smaller in diameter and length compared to the .38 caliber cartridges.
Yes
Typically, they're about even.. the bullet diameter .38 Special is larger by a negligible amount - .357, as opposed to .356 of the 9mm Parabellum.
The 380 ACP, also known as the 9mm Short, 9x17, 9mm Browning, 9mm Kurz and 9mm Corto uses a .355 diameter bullet. The 38 special uses a .357 diameter bullet. Additionally, the 380 ACP is designed for a semi-automatic and the .38 special is designed for a revolver.
You'd think they would be--right? Depending on the tolerances of a particular weapon, you might be able to use SIMILAR projectiles. A .380 caliber is actually has a .355 caliber projectile--so does a 9mm. The typical .38, as in 38 Special is .357 caliber. So, when all is said and done, .355 caliber is smaller than .357 caliber. No, they are not the same, but close.
9 millimeter is the caliber. IMPROVING ANSWER: A "9mm" bullet is actually .355 or .356 of an inch in diameter. So the caliber is about .36, but nobody calls it that because it would be confusing. Everybody calls it a 9mm and if somebody asks you what "caliber" that pistol is, you can answer "It's a 9mm" without having to add or explain anything. further improve: 9mm is the correct answer. you can find the caliber by measuring the diameter of the bullet. translate to millimeters or inches and that's the caliber. 9mm is a 9mm caliber not "around .36"
About .36 caliber. The 9mm family of calibers normally uses a bullet that is .356 diameter. This is the same as the .380 and nearly the same as the .38 Special, whose "nominal" calibers are quite different from their actual bullet diameter when measured.