yolk

American  

[yohk, yohlk] / joʊk, joʊlk /

noun

• yolks
  plural

1. the yellow and principal substance of an egg, as distinguished from the white.

2. Embryology. the part of the contents of the egg of an animal that enters directly into the formation of the embryo, together with any material that nourishes the embryo during its formation.

3. the essential part; the inner core.

4. a natural grease exuded from the skin of sheep.

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yolk British  

/ jəʊk /

noun

1. the substance in an animal ovum consisting of protein and fat that nourishes the developing embryo

2. a greasy substance secreted by the skin of a sheep and present in the fleece

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yolk Scientific  

/ yōk /

1. The yellow internal part of the egg of a bird or reptile. The yolk is surrounded by the albumen and supplies food to the developing young.

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Other Word Forms

Derived Forms

• yolked
  adjective
• yolkless
  adjective
• yolky
  adjective

Inflected Forms

Nouns

• yolks
  plural

Etymology

Origin of yolk

before 1000; Middle English yolke, yelke, Old English geoloca, derivative of geolu yellow

Explanation

A yolk is the inner, yellow part of an egg. If you order eggs "sunny side up," those "suns" are the egg yolks. When a bird lays an egg that's fertilized and begins to grow into a baby bird, the yolk is the substance that nourishes the bird embryo. The eggs we eat have yolks too, but since they are unfertilized, these protein-rich yolks can be beaten into omelettes or mixed into cake batter. The Old English root of yolk, geolca, literally means "the yellow part."

Example Sentences

See Examples For:

yolk yolks

A fried egg is also great if you’re not a fan of a runny yolk.

From Salon ● Jul. 19, 2026

Down the hall, ceramic eggs cover the walls while a giant yolk rests atop a mattress, turning a hospital bed into a commentary on fragility and birth.

From Los Angeles Times ● May 20, 2026

The possible answers were plain flour, salted butter, egg yolk and double cream.

From BBC ● Apr. 26, 2026

A six-minute egg is soft, custardy, a little luxurious — something you eat with toast, standing at the counter, yolk pooling gold across the plate.

From Salon ● Apr. 3, 2026

According to these authors, the delayed but lethal effect on the young birds follows from storage of dieldrin in the yolk of the egg, from which it is gradually assimilated during incubation and after hatching.

From "Silent Spring" by Rachel Carson

To that, add your reserved hard-boiled yolks, blended in until the mixture thickens and turns almost custard-like.

From Salon ● Apr. 14, 2026

In my recipe, I haven’t used as many egg yolks as they do at the restaurant because I don’t want you to be burdened with leftover egg whites.

From The Wall Street Journal ● Mar. 27, 2026

Whisked egg yolks and sugar get spooned on top, like a frothy, golden ambrosia.

From The Wall Street Journal ● Mar. 17, 2026

Foods that provide choline include beef liver, egg yolks, beef, chicken, fish, soybeans and milk, among others.

From Science Daily ● Dec. 4, 2025

Under the frozen heat of his glance they tripped over doorsills and dropped the salt cellar into the yolks of their poached eggs.

From "Song of Solomon" by Toni Morrison