bilirubin vs animal pigment

bilirubin and animal pigment both are nouns.

Word	Noun	Adjective	Verb	Adverb
bilirubin	Yes	No	No	No
animal pigment	Yes	No	No	No

As nouns, animal pigment is a hypernym of bilirubin; that is, animal pigment is a word with a broader meaning than bilirubin:

bilirubin: an orange-yellow pigment in the bile that forms as a product of hemoglobin; excess amounts in the blood produce the yellow appearance observed in jaundice
animal pigment: pigment occurring in animals

bilirubin (noun)	animal pigment (noun)
an orange-yellow pigment in the bile that forms as a product of hemoglobin; excess amounts in the blood produce the yellow appearance observed in jaundice	pigment occurring in animals