Suicide is the practice of taking one's own life.
Although it has much in common with other premature causes of death like homicide and old age, suicide is a self-directed action, while homicide is just a sugarcoated name for murder. Committing suicide is a personal choice that any individual is free to make, just like wearing a certain style of clothing, having an abortion, or running for president. However, unlike running for president, it has no age minimum, and unlike wearing a certain style of clothing, it doesn't involve staying alive. That said, suicide makes considerably more sense for some people than for others. If one is about to be executed by an approaching army, suicide is a clever idea that will surely frustrate them, whereas if one is momentarily distraught because of some minor setback, it's a tossup.