Emphysema is a chronic lung disease and a major subtype of chronic obstructive pulmonary disease (COPD) characterized by damage to the air sacs (alveoli) in the lungs. In emphysema, the walls between many of the alveoli are damaged and break down, resulting in fewer but larger air sacs. This reduces the surface area available for oxygen and carbon dioxide exchange, leading to difficulty breathing and less oxygen being delivered to the bloodstream. The air sacs also lose their elasticity, which makes it harder for the lungs to expel air, causing air to get trapped in the lungs. The main cause of emphysema is long- term exposure to lung irritants, with cigarette smoking being the most common cause. Other contributing factors include exposure to air pollution, chemical fumes, dust, and a rare genetic condition called alpha-1 antitrypsin deficiency. Symptoms often include shortness of breath (especially during physical activity), a chronic cough, wheezing, and fatigue. Over time, breathing difficulties worsen due to progressive lung damage. While there is no cure for emphysema and lung damage is irreversible, treatments such as quitting smoking, medications, inhalers, pulmonary rehabilitation, and oxygen therapy can help manage symptoms and slow disease progression. In summary, emphysema is a progressive lung disease marked by destruction of lung tissue and reduced ability to breathe, most commonly caused by smoking and environmental exposures, and it is a major component of COPD.