Sputum

Mucus or phlegm coughed up from the lower respiratory tract, especially the bronchi and lungs. Possible causes for excessive production are inflammation (COPD, asthma, bronchiectasis, cystic fibrosis), infection (pneumonia, bronchitis, tuberculosis), irritants (cigarette smoke, inhaled dust, air pollutants), allergy, post-nasal drip, acid reflux, or malignancy.