congestion vs symptom

congestion and symptom both are nouns.

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

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

congestion: excessive accumulation of blood or other fluid in a body part
symptom: (medicine) any sensation or change in bodily function that is experienced by a patient and is associated with a particular disease

congestion (noun)	symptom (noun)
excessive accumulation of blood or other fluid in a body part	anything that accompanies X and is regarded as an indication of X's existence
excessive crowding	(medicine) any sensation or change in bodily function that is experienced by a patient and is associated with a particular disease