yolk vs egg yolk

yolk and egg yolk both are nouns.

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

As nouns, yolk and egg yolk are synonyms defined as:

yolk and egg yolk: the yellow spherical part of an egg that is surrounded by the albumen

yolk (noun)	egg yolk (noun)
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
the yellow spherical part of an egg that is surrounded by the albumen