c.1600, from Modern Latin, from Greek pneumonia "inflammation of the lungs," from pneumon "lung," altered (perhaps by influence of pnein "to breathe") from pleumon "lung," literally "floater," probably cognate with Latin pulmo (see pulmonary), from PIE *pleu- "to flow, to swim" (see pluvial). Alteration in Greek perhaps by influence of pnein "to breathe."
pneumonia pneu·mo·nia (nu-mōn'yə, nyu-)
n.
An acute or chronic disease marked by inflammation of the lungs and caused by viruses, bacteria, or other microorganisms and sometimes by physical and chemical irritants.
A disease characterized by inflammation of the lungs. Pneumonia can be caused by many factors, including bacterial infections, viral infections, and the inhalation of chemical irritants.