English-Hanzi/What is pneumonia?

Pneumonia is a lung infection. It affects the tiny airbag of the lungs, called alveoli. When suffering from pneumonia, the airbag is inflamed and filled with liquid, making breathing difficult. 肺炎 是 一种 肺部 感染。 它影响肺部的微小气囊，称为肺泡。患有肺炎时，气囊发炎并充满液体，使呼吸困难。