Differential diagnosis is a systematic method used by healthcare professionals to identify a specific illness or condition among various possibilities. It involves gathering patient information, such as symptoms and medical history, and then comparing these details against a list of potential diagnoses. This process helps ensure that the correct condition is identified and treated appropriately. The goal of differential diagnosis is to narrow down the list of possible conditions to find the most likely cause of a patient's symptoms. This approach is essential in fields like medicine and psychiatry, where similar symptoms can arise from different underlying issues, ensuring accurate and effective treatment.