vitellus vs yolk

vitellus and yolk both are nouns.

Word	Noun	Adjective	Verb	Adverb
vitellus	Yes	No	No	No
yolk	Yes	No	No	No

As nouns, vitellus and yolk are synonyms defined as:

vitellus and yolk: nutritive material of an ovum stored for the nutrition of an embryo (especially the yellow mass of a bird or reptile egg)

vitellus (noun)	yolk (noun)
nutritive material of an ovum stored for the nutrition of an embryo (especially the yellow mass of a bird or reptile egg)	nutritive material of an ovum stored for the nutrition of an embryo (especially the yellow mass of a bird or reptile egg)
	the yellow spherical part of an egg that is surrounded by the albumen