A submachine gun or SMG is a carbine-length, pistol-caliber firearm that is capable of fully automatic fire. Early SMGs such as the MP18 have rifle-like appearance. While more modern models do have features like folding stock, pistol grip and a fire selector. The term "submachine gun" was coined by John T. Thompson, to describe its design concept as an automatic weapon with notably less firepower than a machine gun (hence the prefix "sub-").
A subset of submachine gun is dubbed machine pistol, which are often used to describe a handgun with automatic fire capability (e.g. Glock 18C), or compact SMGs with handgun-like ergonomics (e.g. Micro Uzi).
The following guns are classified as personal defense weapon. Technically an intersection between an SMG and assault rifle. They fire smaller caliber handgun rounds with sharper tips, designed for higher velocity and better penetration against body armor. Such rounds resemble miniature intermediate rifle rounds.
