Empyema

An empyema (/ˌɛmpaɪˈiːmə/) is a collection or gathering of pus within a naturally existing anatomical cavity. The term is most commonly used to refer to pleural empyema, which is empyema of the pleural cavity. It must be differentiated from an abscess, which is a collection of pus in a newly formed cavity. Empyema most commonly occurs as a complication of pneumonia but can also result from other infections or conditions that lead to the collection of infected fluid in a body cavity.

The term is from Greek ἐμπύημα, "abscess".