A normal healthy adult lung is divided into 23 levels of bronchi, from the main bronchi below the larynx to the terminal fine bronchi, just like the bifurcation of a large tree, which is an anatomical concept, while bronchitis is a clinical disease concept. Bronchial coughing, coughing sputum, coughing yellow sputum and even blood in sputum occur after cold, chest imaging easily reveals increased and thickened lung texture bilaterally, and relatively coarse bronchial breath sounds can be heard in both lungs on examination, which can be diagnosed as acute bronchitis when combined with the patient having cold, flu, smoking, etc. If there are similar episodes in the same season every year, with a long history of smoking, accompanied by heart tiredness and wheezing after activity, the patient can be given a diagnosis of chronic bronchitis based on lung function and CT reports. Therefore, bronchus is an anatomical concept and bronchitis is a clinical disease concept, and they are distinct.