Egg (tamago, Kana: たまご Kanji: 卵, in Japanese) is a food product produced from poultry (chicken, duck, quail, goose, etc.) that is used as both an ingredient and a main dish for baked foods. Eggs have a hard shell of calcium carbonate enclosing a liquid white, a single yolk (or an occasional double yolk) and an air cell. The white or albumen is a clear liquid that turns to an opaque white when cooked or beaten. The yolk is orange to yellow in color, and becomes pale yellow when cooked to a solid form. The air cell increases in size as the egg ages and begins to lose moisture, thus decreasing in quality. Eggs can be cooked by boiling, poaching, frying, microwaving, or baking and they are one of the most common ingredients used for a variety of recipes. The types of eggs that are available for food preparation include chicken, duck, goose, turkey, and quail. Ostrich eggs are another variety of egg that is consumed, but are not readily available. Large in size, one ostrich egg equals 2 dozen standard size chicken eggs.
Egg white is the common name for the clear liquid (also called the albumen or the glair/glaire) contained within an egg. The rest of the egg is known as the yolk.
The egg yolk is the yellow inside an egg. Its primary purpose is to serve as a food reserve for the developing embryo. The clear part which surrounds the yolk is known as the egg white or albumen.