A more thorough explanation:

Definition: Sound mind refers to a person's mental ability to understand the nature and effect of their actions. It is often used in the context of testamentary capacity, which is the mental ability required to prepare a valid will.

For example, a person who is suffering from acute pain may have a reduced capacity to understand the admission form of a hospital. In this case, their sound mind is affected by their physical condition.

Sound mind is also important in criminal law, where a person must possess the mental ability to understand right from wrong to be held accountable for a crime. If a person's mental state is impaired due to intoxication, trauma, or disease, they may have diminished capacity, which can be used to determine the degree of the offense or the severity of the punishment.

Overall, sound mind refers to a person's mental ability to make decisions and understand the consequences of their actions.