A yellow phospholipid essential for the metabolism of fats; found in egg yolk and in many plant and animal cells; used commercially as an emulsifier WordNet 3.0 & Open English WordNet

Lecithin is a generic term to designate any group of yellow-brownish fatty substances occurring in animal and plant tissues which are amphiphilic – they attract both water and fatty substances, and are used for smoothing food textures, emulsifying, homogenizing liquid mixtures, and repelling sticking materials. Wikipedia

Generic term for amphiphilic substances of plant and animal origin Wikidata

The principal phospholipid in animals; it is particularly abundant in egg yolks, and is extracted commercially from soy. It is a major constituent of cell membranes, and is commonly used as a food additive (as an emulsifier). Wiktionary

Lecithin. Wiktionary (translation)