Depression is a mood disorder characterized by persistent feelings of sadness, loss of interest or pleasure in activities once enjoyed, and a range of physical and emotional symptoms. These can include changes in appetite or weight, sleep disturbances, fatigue, feelings of worthlessness or guilt, and difficulty concentrating. Depression can vary in severity and duration, affecting daily functioning and quality of life. Causes may involve genetic, biological, environmental, and psychological factors. Treatment typically includes psychotherapy, medication, or a combination of both. Support from loved ones and lifestyle changes such as regular exercise and healthy eating can also aid in managing depression effectively.