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Medical Term:


Pronunciation: yok, yolk


  1. One of the types of nutritive material stored in the oocyte (ovum) for the nutrition of the embryo; yolk is particularly abundant and conspicuous in the eggs of birds.
  2. Fatty material found in the wool of sheep; when extracted and purified, it becomes lanolin.

Synonym(s): vitellus

[A.S. geolca; geolu, yellow]

© Copyright 2017 Wolters Kluwer. All Rights Reserved. Review Date: Sep 19, 2016.