What term refers to the act of ending another person's life painlessly as an act of mercy?

The term that signifies the act of ending another person's life painlessly as an act of mercy is euthanasia. This practice is often discussed in the context of terminal illness or severe suffering where the intent is to alleviate pain and suffering for the individual in question. Euthanasia is typically performed with consent and is viewed by some as a compassionate choice when faced with unbearable conditions that cannot be alleviated through other means.

In contrast, the other options encompass different meanings and contexts. For example, suicide refers to an individual's act of taking their own life, while assisted suicide involves someone actively helping another to end their life, usually due to terminal illness or severe pain, but it does not necessarily carry the same connotations of mercy as euthanasia might. Murder, on the other hand, involves unlawfully taking another person's life with intent to harm and is considered a criminal act. Thus, euthanasia specifically aligns with a merciful intention behind the action.