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,^[1] which is empyema of the pleural cavity. It differs 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.^[2]

The term is from Greek ἐμπύημα, "abscess".