excrement vs dejection

excrement and dejection both are nouns.

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

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

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

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