excrement vs faeces

excrement and faeces both are nouns.

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

As nouns, faeces is a hyponym of excrement; that is, faeces 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
faeces: solid excretory product evacuated from the bowels

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