**Abstract**

Chronic obstructive lung disease (COPD) is heterogeneous and complex. Symptoms and pathophysiological disorders overlap between COPD and asthma. To progress the management of COPD, patients with COPD should be classified by distinct clinical phenotypes. These groupings derived from multiple dimensions including clinical, physiologic, imaging, and endotyping determine clusters of patients with common characteristics that relate to clinically meaningful outcomes such as symptoms, exacerbations, response to therapy, and disease progression (stratified medicine). Moreover, since several phenotypes can coexist in individual patients with COPD, an approach due to therapeutic target identified phenotypes and endotypes (treatable traits) has been proposed as an advanced therapy recently (precision medicine). Airway eosinophilia and airway hyperresponsiveness, which are hallmarks of asthma, are developed in some patients with COPD, independent of asthma. It is perhaps meaningful to classify COPD according to airway eosinophilia and airway hyperresponsiveness as phenotypes and to put these phenotypes into focus as treatable traits. These phenotypes are closely related to frequency of exacerbations and reactivity to inhaled corticosteroids with bronchodilators in therapy for COPD. Hence, research for phenotype classification can play a fundamental role for development of the management and treatment for COPD.

**Keywords:** COPD, phenotypes, treatable traits, airway eosinophilic inflammation, airway hyperresponsiveness
