Hemoptysis is defined as coughing up blood originating below the vocal cords. It can range from blood-streaked sputum to coughing up pure blood. The document discusses the definition, causes, differential diagnosis, diagnosis and treatment of hemoptysis. The main causes discussed are tracheobronchial diseases like bronchitis and tumors, as well as cardiovascular issues. Diagnosis involves history, examination, labs, chest imaging like CXR, CT, and procedures like bronchoscopy.