Vitellum is a term used to describe the yolk of an egg, particularly one that is fertilized. It is an essential part of embryonic development and provides the necessary nutrients for the developing embryo. There are several other terms that can be used as synonyms for vitellum, including yolk, ovum, and egg cell. Additionally, words like oocyte, egg white, albumen, and chalaza can also be associated with various components of an egg. These synonyms are often used interchangeably based on the context and the specific part of the egg that is being referred to.