Used commercially as an emulsifier

• Lipid in blood and eggs - it's found in lichen, unexpectedly
• Found in egg yolk and in many plant and animal cells
• A yellow phospholipid essential for the metabolism of fats
• Fatty compound

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
fatty substance found in the yolks of eggs (among other places), 1861, from French lécithine (coined 1850 by N.T. Gobley), from Greek lekithos "egg yolk," + chemical suffix -ine (2). Greek lekithos is of unknown origin.

Wikipedia Word definitions in Wikipedia
Lecithin (from the Greek lekithos (egg yolk)) 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 so are hydrophilic ) and fatty substances ...

WordNet Word definitions in WordNet
n. 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

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Lecithin \Lec"i*thin\, n. [Gr. le`kiqos the yolk of an egg.] (Physiol. Chem.) A complex, nitrogenous phosphorized substance widely distributed through the animal body, and especially conspicuous in the brain and nerve tissue, in yolk of eggs, and in the ...

Wiktionary Word definitions in Wiktionary
n. (context organic chemistry English) 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). ...