Difference between Sputum and Phlegm

What is the difference between Sputum and Phlegm?

Sputum as a noun is matter coughed up and expectorated from the mouth, composed of saliva and discharges from the respiratory passages such as mucus, phlegm or pus. while Phlegm as a noun is 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.

We hope you now know whether to use Sputum or Phlegm in your sentence.