fecal matter vs faeces

fecal matter and faeces both are nouns.

Word	Noun	Adjective	Verb	Adverb
fecal matter	Yes	No	No	No
faeces	Yes	No	No	No

As nouns, fecal matter and faeces are synonyms defined as:

fecal matter and faeces: solid excretory product evacuated from the bowels

Other synonyms of fecal matter include BM, dejection, faecal matter, feces, ordure, stool.

fecal matter (noun)	faeces (noun)
solid excretory product evacuated from the bowels	solid excretory product evacuated from the bowels