Suicide is the act of killing oneself. The etymology is from the Latin suicidium, from sui caedere, to kill oneself. Depending on societal context, it may be considered an aberration, an illness, or a noble act.
According to the Philosophy of Spinoza, the basic motivation of every life being is to survive, so any idea about destroying oneself has to come from an external source. This is one Western view.
State Shinto, however, held that surrender was dishonorable, while suicide was often a means of restoring honor, or demonstrating sincerity. The Japanese custom of seppuku used an excruciatingly painful method to show that one was not afraid of pain or death.
In modern times, it is thought to result from a mental disorder such as schizophrenia or depression or bipolar disorder, but scientists, including biologists and psychologists, are not sure of what prompts people to take their own lives.
While it is controversial, suicide, possibly assisted suicide, is a choice taken by individuals facing unacceptable pain or loss of function. Even more complex are situations where an individual elects to forgo treatment that might extend life, but does not take an active step to end life.
There have been instances in Greek tragedy when a character in a drama such as the play Agamemnon by Aeschylus in which the character Ajax commits suicide because of shame that he wasn't awarded the shield of Achilles. Romeo and Juliet involves double suicide over forbidden love.
- See also: suicide attack
Suicide may be implicit in a military tactic. The 9-11 Attack necessarily involved the suicides of the hijackers, and it was considered an act of terrorism because civilians were killed. Alternatively, however, the Japanese kamikaze attacked purely military targets, with a frequent motivation being that the pilot would inevitably die in combat, so he would choose to have his death be as destructive to the enemy as possible.