‘咳痰’ is a verb meaning 'to cough up phlegm' — the physical act of expelling mucus from the respiratory tract through coughing. The first character, 咳 (ké), means 'to cough', while the second, 痰 (tán), means 'phlegm' or 'sputum'. Together, they form a compound verb that emphasizes the expulsion of mucus specifically, not just dry coughing. This term is commonly used in clinical and everyday health contexts when describing symptoms of colds, bronchitis, or other respiratory conditions.

Unlike the general verb 咳嗽 (késòu, 'to cough'), 咳痰 highlights the presence and removal of secretions, making it especially relevant in medical assessments or patient self-reports. It’s often paired with adverbs like 频繁地 ('frequently') or 带血 ('with blood') to describe severity. While technically a verb, it can also function as a noun in phrases like '咳痰带血' ('coughing up blood-tinged phlegm').