The main difference between Mucus and Phlegm is that the Mucus is a slippery secretion produced by, and covering, mucous membranes and Phlegm is a liquid secreted by the mucous membranes of mammalians.
Mucus ( MEW-kəss) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It is a viscous colloid containing inorganic salts, antiseptic enzymes (such as lysozymes), immunoglobulins, and glycoproteins such as lactoferrin and mucins, which are produced by goblet cells in the mucous membranes and submucosal glands. Mucus serves to protect epithelial cells (that line the tubes) in the respiratory, gastrointestinal, urogenital, visual, and auditory systems; the epidermis in amphibians; and the gills in fish, against infectious agents such as fungi, bacteria and viruses. The average human nose produces about a liter of mucus per day. Most of the mucus produced is in the gastrointestinal tract.
Bony fish, hagfish, snails, slugs, and some other invertebrates also produce external mucus. In addition to serving a protective function against infectious agents, such mucus provides protection against toxins produced by predators, can facilitate movement and may play a role in communication.
Phlegm (Greek: φλέγμα “inflammation, humour caused by heat”) is a liquid secreted by the mucous membranes of mammals. Its definition is limited to the mucus produced by the respiratory system, excluding that from the nasal passages, and particularly that which is expelled by coughing (sputum). Phlegm is in essence a water-based gel consisting of glycoproteins, immunoglobulins, lipids and other substances. Its composition varies depending on climate, genetics, and state of the immune system. Its color can vary from transparent to pale or dark yellow and green, from light to dark brown, and even to dark grey depending on the constituents.
A slippery secretion from the lining of the mucous membranes.
One of the four humors making up the body in ancient and mediaeval medicine; said to be cold and moist, and often identified with mucus. from 13th c.
Viscid mucus produced by the body, later especially mucus expelled from the bronchial passages by coughing. from 14th c.
A watery distillation, especially one obtained from plant matter; an aqueous solution. from 16th c.
Calmness of temperament, composure; also seen negatively, sluggishness, indifference. from 16th c.
the thick viscous substance secreted by the mucous membranes of the respiratory passages, especially when produced in excessive quantities during a cold.
(in medieval science and medicine) one of the four bodily humours, believed to be associated with a calm, stolid, or apathetic temperament.
calmness of temperament
“phlegm and determination carried them through many difficult situations”