phlegm
Meaning of phlegm: Phlegm is thick mucus produced by the airways, often increasing during infection or irritation and distinct from saliva or nasal discharge.
Definition of phlegm
Phlegm is a thick form of mucus produced by glands lining the airways, including the trachea and the bronchial tubes within the lungs. A small amount of mucus is produced by the airways under normal conditions, helping trap dust, debris, and microorganisms before they reach deeper into the lungs, but the amount and character of this mucus can increase noticeably during illness.
Excess phlegm production commonly occurs with respiratory infections, allergies, irritant exposure such as smoking, and chronic lung conditions, and phlegm is often brought up through coughing, particularly when its volume increases beyond what the airways can clear through normal ciliary movement alone. The color and consistency of phlegm can vary depending on its underlying cause, though appearance alone does not reliably distinguish between different causes.
Phlegm coughed up and examined in a laboratory is generally referred to as sputum, a related but more specific term used when the material is collected for testing rather than simply described as a symptom.
Used in a sentence
The patient described increased phlegm production during the respiratory infection.
Good to know
Phlegm and sputum are closely related but not identical in use, since sputum specifically refers to material coughed up and collected for laboratory examination, while phlegm more broadly describes the symptom itself.
Word origin
Where “phlegm” comes from
Formed from Greek phlegma, meaning inflammation or heat, from phlegein, meaning to burn, reflecting its status as one of the four humors in ancient medical theory.