faeces vs excretion

faeces and excretion both are nouns.

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

As nouns, excretion is a hypernym of faeces; that is, excretion is a word with a broader meaning than faeces:

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

Other hypernyms of faeces include body waste, excrement, excreta, excretory product.

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