1. the yolk of an egg, especially in biological or scientific contexts
Usage: scientific; biology

Examples

• The vitellus provides essential nutrients for the developing embryo.
• Scientists studied the composition of the vitellus in bird eggs.
• The vitellus is rich in proteins and lipids necessary for growth.
• During development, the embryo absorbs nutrients from the vitellus.
• The size of the vitellus varies among different species of birds.
• Researchers examined how toxins affect the vitellus in fish eggs.