A casualty, as a term in military usage, is a person in military service, combatant or non-combatant, who becomes unavailable for duty due to any of several circumstances, including death, injury, illness, capture or desertion. In civilian usage, a casualty is a person who is killed, wounded or incapacitated by some event; the term is usually used to describe multiple deaths and injuries due to violent incidents or disasters. It is sometimes misunderstood to mean "fatalities", but non-fatal injuries are also casualties. Military usage In military usage, a is a person in service killed in action, killed by disease, diseased, disabled by injuries, disabled by psychological trauma, captured, deserted, or missing, but not someone who sustains injuries which do not prevent them from fighting. Any casualty is no longer available for the immediate battle or campaign, the major consideration in combat; the number of casualties is simply the number of members of a unit who are not available for duty. The word has been used in a military context since at least 1513. are civilians killed or injured by military personnel or combatants, sometimes instead referred to by the euphemistic expression "collateral damage". NATO definitions The military organisation NATO uses the following definitions: Casualty In relation to personnel, any person who is lost to his organization by reason of being declared dead, wounded, diseased, detained, captured or missing. Battle casualty Any casualty incurred as the direct result of hostile action, sustained in combat or relating thereto, or sustained going to or returning from a combat mission. Non-battle casualty A person who is not a battle casualty, but who is lost to his organization by reason of disease or injury, including persons dying from disease or injury, or by reason of being missing where the absence does not appear to be voluntary or due to enemy action or to being interned. Other definitions These definitions are popular among military historians. Irrecoverable casualty In relation to personnel, any person killed in action, missing in action or who died of wounds or diseases before being evacuated to a medical installation. Medical casualty In relation to personnel, any person incapacitated by wounds sustained or diseases contracted in a combat zone, as well as any person admitted to a medical installation for treatment or recuperation for more than a day. There is a distinction between combat medical casualty and non-combat medical casualty. The former refers