emulsifier vs lecithin

emulsifier and lecithin both are nouns.

Word	Noun	Adjective	Verb	Adverb
emulsifier	Yes	No	No	No
lecithin	Yes	No	No	No

As nouns, lecithin is a hyponym of emulsifier; that is, lecithin is a word with a more specific, narrower meaning than emulsifier:

emulsifier: a surface-active agent that promotes the formation of an emulsion
lecithin: 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

emulsifier (noun)	lecithin (noun)
a surface-active agent that promotes the formation of an emulsion	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