urine vs excretion

urine and excretion both are nouns.

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

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

urine: liquid excretory product
excretion: waste matter (as urine or sweat but especially feces) discharged from the body

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

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