Lunacy, often referred to as insanity, is a term historically used to describe severe mental illness that affects a person's ability to think clearly, make decisions, or understand reality. It encompasses various psychological disorders, which can lead to erratic behavior, emotional instability, and impaired functioning in daily life. The concept of lunacy has evolved over time, with modern psychology recognizing it as part of a broader spectrum of mental health issues. Conditions such as schizophrenia, bipolar disorder, and severe depression may fall under this umbrella, highlighting the importance of proper diagnosis and treatment for those affected.