Mayonnaise, majɔnɛːz, often abbreviated as mayo, is a sauce. It is a stable emulsion

Emulsion

An emulsion is a mixture of two or more liquids that are normally immiscible . Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion is used when both the dispersed and the...

 of oil

Oil

An oil is any substance that is liquid at ambient temperatures and does not mix with water but may mix with other oils and organic solvents. This general definition includes vegetable oils, volatile essential oils, petrochemical oils, and synthetic oils....

, 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...

 and either vinegar

Vinegar

Vinegar is a liquid substance consisting mainly of acetic acid and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation processes. Slow methods generally are used with traditional...

 or lemon juice

Lemon juice

The lemon fruit, from a citrus plant, provides a useful liquid when squeezed. Lemon juice, either in natural strength or concentrated, is sold as a bottled product, usually with the addition of preservatives and a small amount of lemon oil.-Uses:...

, with many options for embellishment with other herbs and spices. Lecithin

Lecithin

Lecithin is a generic term to designate any group of yellow-brownish fatty substances occurring in animal and plant tissues, and in egg yolk, composed of phosphoric acid, choline, fatty acids, glycerol, glycolipids, triglycerides, and phospholipids .The word lecithin was originally coined in 1847 by...

 in the egg yolk is the emulsifier. Mayonnaise varies in color but is often white, cream, or pale yellow. It may range in texture from that of light cream to thick. In countries influenced by France, mustard

Mustard (condiment)

Mustard is a condiment made from the seeds of a mustard plant...

 is also a common ingredient.