The doctor diagnosed his pneumonitis as being caused by a viral infection.

pneumonitis 是由词根 pneumon-（来自希腊语，表示"肺"）和后缀 -itis（表示"炎症"）组成的医学名词，字面意思是"肺部炎症"。在医学上特指肺组织的炎症反应。