excretion vs fecula

excretion and fecula both are nouns.

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

As nouns, fecula is a hyponym of excretion; that is, fecula 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
fecula: excreta (especially of insects)

excretion (noun)	fecula (noun)
the bodily process of discharging waste matter	excreta (especially of insects)
waste matter (as urine or sweat but especially feces) discharged from the body