excretion vs dejection

excretion and dejection both are nouns.

Word	Noun	Adjective	Verb	Adverb
excretion	Yes	No	No	No
dejection	Yes	No	No	No

As nouns, dejection is a hyponym of excretion; that is, dejection is a word with a more specific, narrower meaning than excretion:

excretion: waste matter (as urine or sweat but especially feces) discharged from the body
dejection: solid excretory product evacuated from the bowels

excretion (noun)	dejection (noun)
the bodily process of discharging waste matter	a state of melancholy depression
waste matter (as urine or sweat but especially feces) discharged from the body	solid excretory product evacuated from the bowels