This essay delves into the classification of mood disorders, tracing their historical context from Hippocrates and Aretaeus to the modern diagnostic criteria outlined in the DSM-5. It highlights the DSM-5's approach, emphasizing its updates, including dimensional measurement, new specifiers, and the inclusion of contemporary depressive issues. The essay discusses the two-week symptom evaluation period, focusing on key symptoms like depressed mood and loss of interest, while also addressing the exclusion criteria related to substance abuse and other mental conditions. Furthermore, it examines the removal of the bereavement exclusion in DSM-5 and the shift towards differentiating between ordinary sadness and clinical conditions. The essay references key publications like those by Surís, Holliday & North, Parker, Regier, Kuhl & Kupfer, and Shelton, providing a comprehensive overview of the evolution and current understanding of mood disorder classification.