Boiled eggs are eggs (typically chicken

Chicken

The chicken is a domesticated fowl, a subspecies of the Red Junglefowl. As one of the most common and widespread domestic animals, and with a population of more than 24 billion in 2003, there are more chickens in the world than any other species of bird...

s' eggs) cooked by immersion in boiling water with their shells unbroken. (Eggs cooked in water without their shells are known as poached egg

Poached egg

A poached egg is an egg that has been cooked by poaching, that is, in water.-Preparation:The egg is cracked into a bowl of any size, and then gently slid into a pan of simmering water and cooked until the egg white has mostly solidified, but the yolk remains soft...

s, while eggs cooked below the boiling temperature, either with or without the shell, are known as coddled eggs.) Hard-boiled eggs are either boiled long enough for the egg white

Egg white

Egg white is the common name for the clear liquid contained within an egg. In chickens it is formed from the layers of secretions of the anterior section of the hen's oviduct during the passage of the egg. It forms around either fertilized or unfertilized egg yolks...

 and then the egg yolk

Egg yolk

An egg yolk is a part of an egg which feeds the developing embryo. The egg yolk is suspended in the egg white by one or two spiral bands of tissue called the chalazae...

 to solidify, or they are left in hot water to cool down, which will gradually solidify them, while a soft-boiled egg yolk, and sometimes even the white, remains at least partially liquid.

The egg timer

Egg timer

An egg-timer is a device the primary function of which is to assist in timing the cooking of eggs. Early designs simply counted down for a specific period of time. Some modern designs are able to time more accurately by depending on water temperature rather than an absolute time...

 was so-named due to its common usage in timing the boiling of eggs.