egg yolk vs yolk

egg yolk and yolk both are nouns.

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

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

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

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