In modern usage, a missile is a self-propelled precision-guided munition system, as opposed to an unguided self-propelled munition, referred to as a rocket (although these too can also be guided). Missiles have four system components: targeting and/or missile guidance, flight system, engine, and warhead. Missiles come in types adapted for different purposes: surface-to-surface and air-to-surface missiles (ballistic, cruise, anti-ship, anti-tank, etc.), surface-to-air missiles (and anti-ballistic), air-to-air missiles, and anti-satellite weapons. All known existing missiles are designed to be propelled during powered flight by chemical reactions inside a rocket engine, jet engine, or other type of engine. Non-self-propelled airborne explosive devices are generally referred to as shells and usually have a shorter range than missiles.
In ordinary British-English usage predating guided weapons, a missile is "any thrown object", such as objects thrown at players by rowdy spectators at a sporting event.〔(Guardian newspaper: "Emmanuel Eboué pelted with missiles while playing for Galatasaray" ) Example of ordinary English usage. In this case the missiles were bottles and cigarette lighters〕
==Etymology and usage==
The word ''missile'' comes from the Latin verb ''mittere'', meaning "to send".
In military usage, munitions projected towards a target are broadly categorised as follows:
* A powered, guided munition that travels through the air or space is known as a ''missile'' (or ''guided missile'')''.''
* A powered, ''un''guided munition is known as a ''rocket''.
* Unpowered munitions not fired from a gun are called ''bombs'' whether guided or not; unpowered, guided munitions are known as ''guided bombs'' or ''smart bombs''.
* Munitions that are fired from a gun are known as ''projectiles'' whether guided or not. If explosive, they are known more specifically as ''shells'' or ''mortar bombs''.
* Powered munitions that travel through water are called ''torpedoes'' (an older usage includes fixed torpedoes, which might today be called ''mines'').
* Hand grenades are not usually classed as missiles.
A common further sub-division is to consider ''ballistic missile'' to mean a munition that follows a ballistic trajectory and ''cruise missile'' to describe a munition that generates lift, similar to an airplane.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』