An injury is a harmful event in which a transfer of energy results in tissue damage [1].

examples include:
falls
motor vehicle collisions
assault with and without weapons
environmental injuries such as drowning
The energy is most commonly in the form of mechanical energy such as in the preceding examples, but can also take the form of thermal or electrical energy in the case of thermal or electrical burns.
Mechanical devices involved in energy transmission, such as a car or weapon, are referred to as vectors [2].
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1. Martinez, R. (1990). "Injury Control: A Primer for Physicians." Annals of Emergency Medicine. 19(1): 72-7.
2. Hargarten, J.W.R.a.S.W. (2002). Principles of the Disease of Injury. Rosen's Emergency Medicine. J.A. Marx. St. Louis, Missouri, Mosby Inc. 1:821-828.