salutation vs greeting

salutation and greeting both are nouns.

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

As nouns, salutation and greeting are synonyms defined as:

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

salutation (noun)	greeting (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