greeting vs salutation

greeting and salutation both are nouns.

Word	Noun	Adjective	Verb	Adverb
greeting	Yes	No	No	No
salutation	Yes	No	No	No

As nouns, greeting and salutation are synonyms defined as:

greeting and salutation: (usually plural) an acknowledgment or expression of good will (especially on meeting)

greeting (noun)	salutation (noun)
(usually plural) an acknowledgment or expression of good will (especially on meeting)	(usually plural) an acknowledgment or expression of good will (especially on meeting)
	an act of honor or courteous recognition
	word of greeting used to begin a letter