The definition of insanity is the state of being severely mentally ill, or the condition of behaving in a way that is unreasonable and not based on good judgment because of a severe mental illness. In popular culture, the phrase “insanity” is often used colloquially to refer to someone or something that is behaving in an unpredictable or erratic manner. However, in a medical context, the term “insanity” is not used as a diagnosis, and mental health professionals generally do not use it to describe mental health conditions. Instead, mental health conditions are diagnosed based on specific criteria and behaviors that are outlined in the diagnostic manuals used by mental health professionals, such as the Diagnostic and Statistical Manual of Mental Disorders (DSM).