purulency vs symptom

purulency and symptom both are nouns.

Word	Noun	Adjective	Verb	Adverb
purulency	Yes	No	No	No
symptom	Yes	No	No	No

As nouns, symptom is a hypernym of purulency; that is, symptom is a word with a broader meaning than purulency:

purulency: symptom of being purulent (containing or forming pus)
symptom: (medicine) any sensation or change in bodily function that is experienced by a patient and is associated with a particular disease

purulency (noun)	symptom (noun)
symptom of being purulent (containing or forming pus)	anything that accompanies X and is regarded as an indication of X's existence
	(medicine) any sensation or change in bodily function that is experienced by a patient and is associated with a particular disease