“Compos mentis” is a Latin phrase that means “of sound mind” or “in possession of one’s faculties” in English. This phrase is commonly used in legal and medical contexts to describe a person who is mentally competent, rational, and capable of making sound decisions. In legal matters, it may be used to determine a person’s ability to understand and participate in legal proceedings or to make important decisions such as signing a contract or a will. In medical contexts, it refers to someone who is mentally stable and not suffering from any severe mental illness or impairment.