Decapitation
Decapitation is the complete separation of the head from the body. Such an injury is always fatal to humans and animals, since it deprives all other organs of the involuntary functions that are needed for the body to function, while the brain is deprived of oxygenated blood and blood pressure.
The term beheading refers to the act of deliberately decapitating a person, either as a means of murder or execution; it may be accomplished with an axe, sword, knife, or by mechanical means such as a guillotine. An executioner who carries out executions by beheading is called a headsman.