goop vs sapropel

goop and sapropel both are nouns.

Word	Noun	Adjective	Verb	Adverb
goop	Yes	No	No	No
sapropel	Yes	No	No	No

As nouns, sapropel is a hyponym of goop; that is, sapropel is a word with a more specific, narrower meaning than goop:

goop: any thick, viscous matter
sapropel: sludge (rich in organic matter) that accumulates at the bottom of lakes or oceans

goop (noun)	sapropel (noun)
street names for gamma hydroxybutyrate	sludge (rich in organic matter) that accumulates at the bottom of lakes or oceans
any thick, viscous matter