Euthanasia is the intentional killing by act or omission of a dependent human being for his or her alleged benefit.
Euthanasia can be an action (act of commission), i.e. lethal injection, shooting, smothering. This is sometimes referred to as direct or positive euthanasia.
Euthanasia can also an omission, such as intentionally causing death by withholding or withdrawing necessary and ordinary (usual and customary) care or food and water. This is sometimes referred to as indirect or passive euthanasia.
If an action or omission is intended to cause the death of a person, there is no moral distinction between them. The victim is equally as dead.
Euthanasia can be voluntary – that is, the person gives consent to be killed. Or, it can be involuntary – that is, the person who is killed is incapable of giving consent or does not give consent.
Assisted suicide – Suicide is the taking of one’s own life. In assisted suicide, which is a form of euthanasia, someone provides an individual with the information, guidance, and means to take his own her own life.
Source: Human Life Alliance – www.humanlife.org