Cough is classified according to its performance characteristics in terms of its course, nature, duration and rhythm, which are important for the diagnosis of the disease: I. Course of cough: 1. Acute cough: Duration <3 weeks; Acute cough: Common cold is the most common cause of acute cough, other causes include acute bronchitis, acute sinusitis, allergic rhinitis, acute attacks of chronic bronchitis, bronchial asthma, etc. 2. Subacute cough: 3-8 weeks, the most common causes are post-cold cough (also known as post-infectious cough), sinusitis, bronchial asthma, etc. 3. Chronic cough: ≥ 8 weeks, with common causes such as chronic bronchitis, bronchiectasis, endobronchial tuberculosis, pneumonia, tuberculosis, lung cancer, asthma, postnasal drip syndrome, gastroesophageal reflux cough, psychogenic cough, etc. Second, the nature of cough: 1. Dry cough: cough without sputum as dry cough, irritating dry cough is mostly seen in chronic laryngitis, bronchial foreign bodies or tumors, mild tuberculosis of the nucleus or endobronchial lining, pleurisy, external ear irritation, etc.; mycoplasma infection of the lung can also cause a longer irritating cough. Drugs used to treat hypertension, such as captopril and enalapril, have the side effect of causing a dry cough. 2. Wet cough: cough with phlegm is a wet cough, mostly seen in bronchial infections, bronchial dilatation, pneumonia, lung abscess, tuberculosis with cavities, etc. This is due to the position. When lying down, bronchial secretions are retained in the bronchi, and when rising in the morning, the bronchi are stimulated to cough in order to discharge the secretions. 2. Nocturnal cough: Nocturnal cough is mostly seen in patients with tuberculosis and chronic left heart insufficiency. The cough intensifies at night when lying down, related to position change and sputum stimulation, and is mostly seen in patients with chronic inflammation of the upper respiratory tract, chronic bronchial or bronchial dilatation, with the same meaning as morning cough; 4. Cough rhythm: 1. mono-cough, seen in patients with laryngitis, bronchitis, smoking and early tuberculosis; 2. paroxysmal and spasmodic cough, seen in foreign body aspiration, whooping cough, asthma, endobronchial tuberculosis and bronchial tumors; 3. Continuous cough, mostly seen in bronchial and pulmonary inflammation.