.医学英语口语：肺炎 pneumonia alternative names pneumonitis; bronchopneumonia; community-acquired pneumonia definition pneumonia is an inflammation of the lungs caused by an infection. many different organisms can cause it, including bacteria, viruses, and fungi. pneumonia is a common illness that affects millions of people each year in the united states. pneumonia can range from mild to severe, even fatal. the severity depends on the type of organism causing pneumonia as well
