Nutritive material, rich in protein and fats, found within the ovum to supply nourishment for the developing embryo. It is nearly absent in the ova of humans and other mammals, in whom the embryo receives nourishment from the mother, through the placenta.
A substance, rich in protein and fat, that is laid down within the egg cell as nourishment for the embryo. It is absent (or nearly so) from the eggs of mammals (including man) whose embryos absorb nutrients from their mother.
The contents of the ovum; sometimes only the nutritive portion.
The yolk of an egg is suspended within the egg white, also known as albumen. It is the substance within the egg or ovum that provides nourishment during the initial phases of embryo development.