purulent pleurisy vs empyema

purulent pleurisy and empyema both are nouns.

Word	Noun	Adjective	Verb	Adverb
purulent pleurisy	Yes	No	No	No
empyema	Yes	No	No	No

As nouns, empyema is a hypernym of purulent pleurisy; that is, empyema is a word with a broader meaning than purulent pleurisy:

purulent pleurisy: a collection of pus in the lung cavity
empyema: a collection of pus in a body cavity (especially in the lung cavity)

Other hypernyms of purulent pleurisy include pleurisy.

purulent pleurisy (noun)	empyema (noun)
a collection of pus in the lung cavity	a collection of pus in a body cavity (especially in the lung cavity)